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1

Flushing submarine canyons  

Microsoft Academic Search

The continental slope is a steep, narrow fringe separating the coastal zone from the deep ocean. During low sea-level stands, slides and dense, sediment-laden flows erode the outer continental shelf and the continental slope, leading to the formation of submarine canyons that funnel large volumes of sediment and organic matter from shallow regions to the deep ocean1. During high sea-level

Miquel Canals; Pere Puig; Xavier Durrieu de Madron; Serge Heussner; Albert Palanques; Joan Fabres

2006-01-01

2

Influence of San Gabriel submarine canyon on narrow-shelf sediment dynamics, southern California  

USGS Publications Warehouse

A conceptual model attributes the PTC to modification of shelf circulation patterns by San Gabriel Canyon. Surface waves diverge over the canyon head resulting in differential wave set up at the shore face. This forces back turbid nearshore water for a distance of a few kilometers toward the canyon. At some point on the shelf, seaward nearshore flow overlaps offshore currents generated or modified by internal waves focused onto the shelf by the canyon and/or turbulent eddies produced by flow separation in currents moving across the canyon axis. At times, these subtle processes overprint tidal and wind-driven currents and thereby create the PTC. The model suggests that canyons heading several kilometers from shore can have a regulatory effect on narrow-shelf sediment dynamics.

Karl, Herman A.

1980-01-01

3

Sedimentary facies in submarine canyons  

NASA Astrophysics Data System (ADS)

Submarine canyons are the major conduits by which sediment, pollutants and nutrients are transported from the continental shelf out into the deep sea. The sedimentary facies within these canyons are remarkably poorly understood because it has proven difficult to accurately sample these heterogeneous and bathymetrically complex environments using traditional ship-based coring techniques. This study exploits a suite of over 100 precisely located vibracores collected using remotely operated vehicles in ten canyons along the northern Californian margin, enabling better understanding of the facies that exist within submarine canyons, their distribution, and the processes responsible for their formation. The dataset reveals three major facies types within the submarine canyons: extremely poorly sorted, coarse-grained sands and gravels with complex and indistinct internal grading patterns and abundant floating clasts; classical normally graded thin bedded turbidites; and a variety of fine-grained muddy deposits. Not all facies are observed within individual canyons, in particular coarse-grained deposits occur exclusively in canyons where the canyon head cuts up to the modern day beach, whereas finer grained deposits have a more complex distribution that relates to processes of sediment redistribution on the shelf. Pairs of cores collected within 30 meters elevation of one another reveal that the coarse-grained chaotic deposits are restricted to the basal canyon floor, with finer-grained deposits at higher elevations on the canyon walls. The remarkable heterogeneity of the facies within these sediment cores illustrate that distinctive processes operate locally within the canyon. In the authors' experience the canyon floor facies represent an unusual facies rarely observed in ancient outcrops, which potentially results from the poor preservation of ancient coarse-grained canyon deposits in the geological record.

Sumner, E.; Paull, C. K.; Gwiazda, R.; Anderson, K.; Lundsten, E. M.; McGann, M.

2013-12-01

4

Plunge Pools in Submarine Canyons  

NASA Astrophysics Data System (ADS)

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

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

2002-12-01

5

Currents in monterey submarine canyon  

USGS Publications Warehouse

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 in the shallow reaches (100-m amplitude isotherm oscillations and associated high-speed rectilinear currents. The 15-day spring-neap cycle and a ???3-day??? band are the two prominent frequencies in subtidal flow field. Neither of them seems directly correlated with the spring-neap cycle of the sea level.

Xu, J.P.; Noble, M.A.

2009-01-01

6

Primary Initiation of Submarine Canyons  

E-print Network

The discovery of close-to-star gas-giant exo-planets lends support to the idea of Earth's origin as a Jupiter-like gas-giant and to the consequences of its compression, including whole-Earth decompression dynamics that gives rise, without requiring mantle convection, to the myriad measurements and observations whose descriptions are attributed to plate tectonics. I propose here another, unanticipated consequence of whole-Earth decompression dynamics: namely, a specific, dominant, non-erosion, underlying initiation-mechanism precursor for submarine canyons that follows as a direct consequence of Earth's early origin as a Jupiter-like gas-giant.

Herndon, J Marvin

2011-01-01

7

Primary Initiation of Submarine Canyons  

E-print Network

The discovery of close-to-star gas-giant exo-planets lends support to the idea of Earth's origin as a Jupiter-like gas-giant and to the consequences of its compression, including whole-Earth decompression dynamics that gives rise, without requiring mantle convection, to the myriad measurements and observations whose descriptions are attributed to plate tectonics. I propose here another, unanticipated consequence of whole-Earth decompression dynamics: namely, a specific, dominant, non-erosion, underlying initiation-mechanism precursor for submarine canyons that follows as a direct consequence of Earth's early origin as a Jupiter-like gas-giant.

J. Marvin Herndon

2011-02-02

8

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

9

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

10

Plunge Pools in Hawaiian Submarine Canyons  

NASA Astrophysics Data System (ADS)

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

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

2001-12-01

11

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

12

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 (Northwest Mediterranean) was used for topographic and initial forcing conditions. Fourteen scenarios were modelled with varying forcing conditions. Rossby number and Burger number 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. 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 were explained within this new dynamic framework.

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

2014-05-01

13

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

14

Contemporary Sediment-Transport Processes in Submarine Canyons  

NASA Astrophysics Data System (ADS)

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.

Puig, Pere; Palanques, Albert; Martín, Jacobo

2014-01-01

15

A submarine canyon as the cause of a mud volcano Liuchieuyu Island in Taiwan  

E-print Network

A submarine canyon as the cause of a mud volcano Ð Liuchieuyu Island in Taiwan J. Chowa,*, J, we also discuss the relationship between a nearby submarine canyon (Kaoping Submarine Canyon¯ection; Submarine canyon; Mud volcano 1. Introduction In the early Pliocene, the paleoenvironment of the offshore

Lin, Andrew Tien-Shun

16

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

E-print Network

Geomorphic characterization of four shelf-sourced submarine canyons along the U.S. Mid Washington Canyon Norfolk Canyon Turbidity flow a b s t r a c t Shelf-sourced submarine canyons are common of major submarine canyons. Submarine canyons on passive margins are primarily the result of erosion

ten Brink, Uri S.

17

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

18

A submarine canyon conduit under typhoon conditions off Southern Taiwan  

Microsoft Academic Search

The function of a submarine conduit under typhoon conditions is examined. The study site is the Kao-ping river, shelf, and submarine canyon (KPRSC) system located off southern Taiwan on a wave-dominated microtidal coast. The head of the canyon is located approximately 1km off the river mouth. Two comprehensive 1-month field experiments were carried out in 2000 and 2002 during the

James T. Liu; Hui-Ling Lin; Jia-Jang Hung

2006-01-01

19

Sediment Flux in Hueneme and Mugu Submarine Canyons  

Microsoft Academic Search

Subsurface moorings were deployed at ~190 m water depth for 6 months (9\\/07 - 3\\/08) inside Hueneme and Mugu submarine canyons in southern California. Data collected from the sediment traps, located at 30 and 60 meters above canyon floor, showed marked temporal and spatial variations of sediment flux. Not surprisingly, high sediment flux correlated well with high river discharge, which

J. Xu; P. Swarzenski; M. Noble; A. Li

2008-01-01

20

Depositional framework and genesis of Wilcox Submarine Canyon systems, Northwest Gulf Coast  

SciTech Connect

Wilcox (late Paleocene-early Eocene) slope systems of the Texas coastal plain contain two families of paleosubmarine canyons that exhibit distinctly different characteristics and stratigraphic settings: Yoakum and Lavaca type canyons occur as widely separated features within the generally retrogradational middle Wilcox interval. Four such canyons exhibit high length to width ratios, extend far updip of the contemporaneous shelf edge, were excavated deeply into paralic and coastal-plain deposits, and were filled primarily by mud. Fills consist of a lower onlapping unit and capping progradational deposits that are genetically related to deposition of the upper Wilcox fluvial-deltaic sequence. Significantly, the canyon fills correlate with widespread transgressive marine mudstones (the Yoakum shale-Sabinetown Formation and ''Big Shale''). In contrast, Lavaca-type canyons form a system of erosional features created along the rapidly prograding, unstable lower Wilcox continental margin. Comparative analysis of the two canyon system suggests a general process model for submarine canyon formation on prograding basin margins. Key elements are depositional loading of the continental margin creating instability, initiation of a large-scale slump, family of slumps, or listric bedding-plane fault creating a depression or indentation in the margin, and headward and lateral expansion of the depression by slumping and density-underflow erosion. Extent of canyon evolution varies according to time and submerged space available for maturation; short, broad canyons form on narrow shelves of actively prograding margins, and elongate mature canyons form in retrogradational or transgressive settings.

Galloway, W.F.; Dinqus, W.F.; Paige, R.E.

1988-01-01

21

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

22

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

E-print Network

Morphotectonics and incision of the Kaoping submarine canyon, SW Taiwan orogenic wedge Cheng February 2006 Available online 24 March 2006 Abstract The Kaoping submarine canyon developed on the frontal; Incision; Submarine canyon; Taiwan 1. Introduction 1.1. Geological settings The island of Taiwan is located

Lin, Andrew Tien-Shun

23

Origin of Izu-Bonin forearc submarine canyons  

SciTech Connect

Submarine canyons on the Izu-Bonin forearc are morphologically divided from north to south into four types based on their morphology, long profiles, and seismic profiles: Mikura, Aogashima, Sofu, and Chichijima types, respectively. These types of canyons are genetically different from each other. Mikura group is formed by the faults related to bending of the subducting Philippine Sea Plate. Aogashima type genetically relates to the activity of large submarine calderas that supply large amounts of volcaniclastic material to the consequent forearc slope. The third, Sofu group, is thought to be formed by the large-scale mega mass wasting in relation to the recent movement of the Sofugan tectonic line. The last, Chichijima group, is formed by collision of the Uyeda Ridge and the Ogasawara Plateau on the subducting Pacific Plate with Bonin Arc. Long profiles of four types of submarine canyons also support this.

Fujioka, Kantaro (Univ. of Tokyo (Japan)); Yoshida, Haruko (Chiba Univ. (Japan))

1990-06-01

24

Sand Wave Migrations Within Monterey Submarine Canyon, California  

NASA Astrophysics Data System (ADS)

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

Xu, J.; Wong, F. L.

2006-12-01

25

Observations of upwelling events in the Petacalco submarine canyon  

NASA Astrophysics Data System (ADS)

The head of the Petacalco canyon is located in the Petacalco Bay, in the Pacific Ocean (ca. 18N and 102W). The bathymetry of this submarine canyon, close to the head, shows steep slopes from the crests to the bottom and an average along axis slope of 6% within the studied region. The extension of this canyon goes as far as 110 km offshore, reaching the Central America Trench at 4600 m depth. The importance of the canyon in the region is mainly noticeable by the high fishing activity. Besides the windriven upwelling due to Ekman transport near coastal regions, the presence of the canyon enhances the upwelling of deep water from the adjacent oceanic region bringing the nutrients, which are injected into the bay, enhancing primary productivity, very much desire by fishery activities. During, at least six CTD surveys in the area, strong upwelling has been noticed, based on those observations a later survey was designed covering the Petacalco canyon with much larger spatial resolution. Along with those measurements, two thermistor arrays were deployed on the SW crest of the canyon at depths of approximately 60 [m], two ADCP current meters were deployed at 20 [m] depth on the opposite sides of the canyon's axis close to the head of the canyon. Figure 1 shows the CTD stations network and the location of all the instruments. The observations, from the thermistor arrays, show that temperature variations, at a given depth, could span ranges from 28 to 14 Celsius (during the fall period of September 2010). This variations, suggest the presence of internal waves; submarine canyons act as regions of enhanced mixing with focusing and amplification of internal waves. Individual profiles of potential density in the water column show, just below the thermocline, the existence of overturns just over the rim of the canyon suggesting turbulent mixing processes due to possible breakage of internal waves.

Ruiz-Angulo, A.; Zavala-Hidalgo, J.

2011-12-01

26

Anatomy of La Jolla submarine canyon system; offshore southern California  

USGS Publications Warehouse

An autonomous underwater vehicle (AUV) carrying a multibeam sonar and a chirp profiler was used to map sections of the seafloor within the La Jolla Canyon, offshore southern California, at sub-meter scales. Close-up observations and sampling were conducted during remotely operated vehicle (ROV) dives. Minisparker seismic-reflection profiles from a surface ship help to define the overall geometry of the La Jolla Canyon especially with respect to the pre-canyon host sediments. The floor of the axial channel is covered with unconsolidated sand similar to the sand on the shelf near the canyon head, lacks outcrops of the pre-canyon host strata, has an almost constant slope of 1.0° and is covered with trains of crescent shaped bedforms. The presence of modern plant material entombed within these sands confirms that the axial channel is presently active. The sand on the canyon floor liquefied during vibracore collection and flowed downslope, illustrating that the sediment filling the channel can easily fail even on this gentle slope. Data from the canyon walls help constrain the age of the canyon and extent of incision. Horizontal beds of moderately cohesive fine-grained sediments exposed on the steep canyon walls are consistently less than 1.232 million years old. The lateral continuity of seismic reflectors in minisparker profiles indicate that pre-canyon host strata extend uninterrupted from outside the canyon underneath some terraces within the canyon. Evidence of abandoned channels and point bar-like deposits are noticeably absent on the inside bend of channel meanders and in the subsurface of the terraces. While vibracores from the surface of terraces contain thin (< 10 cm) turbidites, they are inferred to be part of a veneer of recent sediment covering pre-canyon host sediments that underpin the terraces. The combined use of state of the art seafloor mapping and exploration tools provides a uniquely detailed view of the morphology within an active submarine canyon.

Paull, C.K.; Caress, D.W.; Lundsten, E.; Gwiazda, R.; Anderson, K.; McGann, M.; Conrad, J.; Edwards, B.; Sumner, E.J.

2013-01-01

27

Physical modeling of tidal resonance in a submarine canyon  

NASA Astrophysics Data System (ADS)

Current 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

28

Evolution of surface gravity waves over a submarine canyon  

E-print Network

The effects of a submarine canyon on the propagation of ocean surface waves are examined with a three-dimensional coupled-mode model for wave propagation over steep topography. Whereas the classical geometrical optics approximation predicts an abrupt transition from complete transmission at small incidence angles to no transmission at large angles, the full model predicts a more gradual transition with partial reflection/transmission that is sensitive to the canyon geometry and controlled by evanescent modes for small incidence angles and relatively short waves. Model results for large incidence angles are compared with data from directional wave buoys deployed around the rim and over Scripps Canyon, near San Diego, California, during the Nearshore Canyon Experiment (NCEX). Wave heights are observed to decay across the canyon by about a factor 5 over a distance shorter than a wavelength. Yet, a spectral refraction model predicts an even larger reduction by about a factor 10, because low frequency components c...

Magne, R; Herbers, T H C; Ardhuin, F; O'Reilly, W C; Rey, V; Magne, Rudy; Belibassakis, Kostas; Herbers, Thomas H. C.; Ardhuin, Fabrice; Reilly, William C. O'; Rey, Vincent

2006-01-01

29

Geology and biology of Oceanographer submarine canyon.  

USGS Publications Warehouse

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

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

1980-01-01

30

Space-for-time substitution and the evolution of a submarine canyon-channel system in a passive progradational margin  

NASA Astrophysics Data System (ADS)

Space-for-time substitution is a concept that has been widely applied, but not thoroughly tested, in some fields of geomorphology. The objective of this study is to test whether the concept of space-for-time substitution is valid in reconstructing the evolution of a submarine canyon-channel system in a passive progradational margin. We use multibeam echosounder data and in situ measurements from the south Ebro Margin to analyse the morphology and morphometry of a sequence of submarine valleys ordered in terms of increasing valley thalweg length. The morphological model of submarine valley evolution that we can propose from this analysis is very similar to established models in the literature, which leads us to conclude that time can be substituted by space when reconstructing the evolution of submarine canyon and channel systems in the south Ebro Margin. By extracting morphometric information from the application of the space-for-time substitution model to our data, we identify a series of morphological patterns as a submarine canyon evolves in a passive progradational margin. These include the geometric similarity of canyon planform shape, an increase in canyon draining efficiency and in the influence of flank slope failures, and an evolution towards equilibrium between canyon form and imposed water and sediment load without net erosion or deposition taking place. We also observe that canyon elongation is higher downslope and that the canyon undergoes an early stage of rapid incision similar to the process of "erosion narrowing" reported in terrestrial rivers. We demonstrate that the conclusions of our study are not limited to submarine valleys in the south Ebro Margin but are applicable to other margins around the world.

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

2014-09-01

31

Giant submarine canyons: is size any clue to their importance in the rock record?  

USGS Publications Warehouse

Submarine canyons are the most important conduits for funneling sediment from continents to oceans. Submarine canyons, however, are zones of sediment bypassing, and little sediment accumulates in the canyon until it ceases to be an active conduit. To understand the potential importance in the rock record of any given submarine canyon, it is necessary to understand sediment-transport processes in, as well as knowledge of, deep-sea turbidite and related deposits that moved through the canyons. There is no straightforward correlation between the final volume of the sedimentary deposits and size o fthe associated submarine canyons. Comparison of selected modern submarine canyons together with their deposits emphasizes the wide range of scale differences between canyons and their impact on the rock record. Three of the largest submarine canyons in the world are incised into the Beringian (North American) margin of the Bering Sea. Zhemchug Canyon has the largest cross-section at the shelf break and greatest volume of incision of slope and shelf. The Bering Canyon, which is farther south in the Bering Sea, is first in length and total area. In contrast, the largest submarine fans-e.g., Bengal, Indus, and Amazon-have substantially smaller, delta-front submarine canyons that feed them; their submarine drainage areas are one-third to less than one-tenth the area of Bering Canyon. some very large deep-sea channells and tubidite deposits are not even associated with a significant submarine canyon; examples include Horizon Channel in the northeast Pacific and Laurentian Fan Valley in the North Atlantic. Available data suggest that the size of turbidity currents (as determined by volume of sediment transported to the basins) is also not a reliable indicator of submarine canyon size.

Normark, William R.; Carlson, Paul R.

2003-01-01

32

Sediment Flux in Hueneme and Mugu Submarine Canyons  

NASA Astrophysics Data System (ADS)

Subsurface moorings were deployed at ~190 m water depth for 6 months (9/07 - 3/08) inside Hueneme and Mugu submarine canyons in southern California. Data collected from the sediment traps, located at 30 and 60 meters above canyon floor, showed marked temporal and spatial variations of sediment flux. Not surprisingly, high sediment flux correlated well with high river discharge, which occurs mostly during episodic winter storms and precipitation, from Santa Clara River, ~12 km upcoast of Hueneme Canyon, and Calleguas Creek, which empties directly into Mugu Canyon. But the observation that both of the Hueneme traps had much higher sediment flux than the Mugu traps was unexpected, because the Mugu canyon head is right next to the mouth of Calleagus Creek whereas the Hueneme canyon is more than 12 km from either Calleguas Creek or Santa Clara River. In this presentation we attempt to characterize the relationships between sediment flux and turbidity current pulses, whose down-canyon speed exceeded 250 cm/s. These pulses seem closely correlated with high waves in the region. We will also describe and discuss the grain size, isotope, and mineral properties of the sediment during high sediment flux events and relate these fluxes to different sediment sources.

Xu, J.; Swarzenski, P.; Noble, M.; Li, A.

2008-12-01

33

Submarine canyons as important habitat for cetaceans, with special reference to the Gully: A review  

NASA Astrophysics Data System (ADS)

There has been much research interest in the use of submarine canyons by cetaceans, particularly beaked whales (family Ziphiidae), which appear to be especially attracted to canyon habitats in some areas. However, not all submarine canyons are associated with large numbers of cetaceans and the mechanisms through which submarine canyons may attract cetaceans are not clearly understood. This paper reviews some of the cetacean associations with submarine canyons that have been anecdotally described or presented in scientific literature and discusses the physical, oceanographic and biological mechanisms that may lead to enhanced cetacean abundance around these canyons. Particular attention is paid to the Gully, a large submarine canyon and Marine Protected Area off eastern Canada for which there exists some of the strongest evidence available for submarine canyons as important cetacean habitat. Studies demonstrating increased cetacean abundance in the Gully and the processes that are likely to attract cetaceans to this relatively well-studied canyon are discussed. This review provides some limited evidence that cetaceans are more likely to associate with larger canyons; however, further studies are needed to fully understand the relationship between the physical characteristics of canyons and enhanced cetacean abundance. In general, toothed whales (especially beaked whales and sperm whales) appear to exhibit the strongest associations with submarine canyons, occurring in these features throughout the year and likely attracted by concentrating and aggregating processes. By contrast, baleen whales tend to occur in canyons seasonally and are most likely attracted to canyons by enrichment and concentrating processes. Existing evidence thus suggests that at least some submarine canyons are important foraging areas for cetaceans, and should be given special consideration for cetacean conservation and protection.

Moors-Murphy, Hilary B.

2014-06-01

34

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

E-print Network

The e¡ect of a submarine canyon on the river sediment dispersal and inner shelf sediment movements 2001 Abstract This study examines the influence of a submarine canyon on the dispersal of sediments the head region of the Kao-ping Submarine Canyon whose landward terminus is located approximately 1 km

Lin, Andrew Tien-Shun

35

Origin of Florida Canyon and the role of spring sapping on the formation of submarine box canyons  

USGS Publications Warehouse

Florida Canyon, one of a series of major submarine canyons on the southwestern edge of the Florida Platform, was surveyed using GLORIA, SeaBeam, and Deep-Tow technologies, and it was directly observed during three DSRV Alvin dives. Florida Canyon exhibits two distinct morphologies: a broad V-shaped upper canyon and a deeply entrenched, flat-floored, U-shaped lower canyon. The flat- floored lower canyon extends 20 km into the Florida Platform from the abyssal Gulf. The lower canyon ends abruptly at an ?3 km in diameter semicircular headwall that rises 750 m with a >60° slope angle to the foot of the upper canyon. The sides of the lower canyon are less steep than its headwall and are characterized by straight faces that occur along preferred orientations and indicate a strong joint control. The upper canyon is characterized by a gently sloping, straight V-shaped central valley cut into a broad terrace. The flat floor of the upper canyon continues as terraces along the upper walls of the lower canyon. On the flanks of the upper canyon, there are five >50-m-deep, >0.5-km-wide, closed sink-hole-like depressions which indicate subsurface dissolution within the platform. The origin of the lower canyon is difficult to explain with traditional models of submarine canyon formation by external physical processes. The movement of ground water, probably with high salinities and reduced compounds along regional joints, may have focused the corrosive force of submarine spring sapping at the head of the lower canyon to produce the canyon's present shape.

Paull, Charles K.; Spiess, Fred N.; Curray, Joseph R.; Twichell, David C.

1990-01-01

36

SCLERACTINIAN CORAL RECRUITMENT PATTERNS AT SALT RIVER SUBMARINE CANYON  

Microsoft Academic Search

Abstract. 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,pop- ulation within quadrats were Agaricia agaricites, Porites astreoides, Madracis decactis, Stephanocoenia michelinii, and,A

St. Croix; Caroline S. Rogers; H. Carl Fitz III; Marcia Gilnack; James Beets; John Hardin

37

Significance of the fine drainage pattern for submarine canyon evolution: The Foix Canyon System, Northwestern Mediterranean Sea  

NASA Astrophysics Data System (ADS)

Submarine gullies are relatively small valleys that occur in a variety of submarine slopes. They are very common in continental slopes and in submarine canyon heads and flanks, where they often form tributary networks. Gullies are smaller than submarine canyons, though there is no standardised size criterion to distinguish between them. Gullies and gully networks have been often viewed as initial steps in the development of larger submarine canyons and more mature drainage networks. The shelf-incising submarine Foix Canyon System (FCS) is located in the northwestern Mediterranean Sea. Numerous, well-developed and morphologically diverse gullies carve its two heads and flanks. The objective of this study is to analyse the drainage network of the FCS and decipher the role of gullies in its evolution. Submarine gully and canyon networks were extracted from swath bathymetry data of 50 m grid size using Geographic Information Systems (GIS). A systematic morphometric analysis was carried out on drainage network of the FCS by using the Horton-Strahler method. Our results show that the FCS is formed by 1660 streams, 1000 km in total length, which can be classified to six stream orders. To detect relevant morphological changes along valley sections, the drainage density, the stream frequency and the drainage area relief parameters were applied. Furthermore, a branching index (Ib) was developed to characterise the geometry of the submarine drainage network. In the canyon heads Ib values are ~ 1.7, which correspond to a dendritic network, whereas Ib in the canyon branches displays values of ~ 2.2 corresponding to a pinnate one. At a finer scale, we have identified two types of canyon flank gullies, namely "rim gullies" and "toe gullies": (1) rim gullies form large, dendritic networks that extend from the canyon thalweg up to the canyon rim, and (2) toe gullies form smaller pinnate networks restricted to the lower part of the canyon flanks. The formation and development of rim gullies are interpreted as the main process responsible for canyon head growth and across-flank transport of material from the continental shelf. Toe gullies, on the other hand, are the morphological expression of the rejuvenation of rim gullies and the canyon itself. Axial incision and toe gully formation are interpreted as the result of bottom-to-top erosive processes acting at different scales, in response to regional and local changes of the factors controlling the system, respectively. This study helps to identify a variety of gullies and the processes they result from and provides a morphometric methodology to characterise submarine drainage networks at fine resolution scales.

Tubau, Xavier; Lastras, Galderic; Canals, Miquel; Micallef, Aaron; Amblas, David

2013-02-01

38

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

39

Evidence of a turbidity current in Monterey Submarine Canyon associated with the 1989 Loma Prieta earthquake  

Microsoft Academic Search

Evidence of a turbidity current sweeping through the Monterey Submarine Canyon following the October 1989 Loma Prieta earthquake was documented by the movement of bottom-deployed acoustic transponders used to navigate free-falling oceanographic instrumentation. Measuring sites located along the Canyon at distances of 55, 130 and 190 km from the Canyon head off Moss Landing, CA, all showed evidence of tectonically

Newell Garfield; Thomas A. Rago; Kurt J. Schnebele; Curtis A. Collins

1994-01-01

40

Ascension Submarine Canyon, California - Evolution of a multi-head canyon system along a strike-slip continental margin  

USGS Publications Warehouse

Ascension Submarine Canyon, which lies along the strike-slip (transform) dominated continental margin of central California, consists of two discrete northwestern heads and six less well defined southeastern heads. These eight heads coalesce to form a single submarine canyon near the 2700 m isobath. Detailed seismic stratigraphic data correlated with 19 rock dredge hauls from the walls of the canyon system, suggest that at least one of the two northwestern heads was initially eroded during a Pliocene lowstand of sea level ???3.8 m.y. B.P. Paleogeographic reconstructions indicate that at this time, northwestern Ascension Canyon formed the distal channel of nearby Monterey Canyon and has subsequently been offset by right-lateral, strike-slip faulting along the San Gregorio fault zone. Some of the six southwestern heads of Ascension Canyon may also have been initially eroded as the distal portions of Monterey Canyon during late Pliocene-early Pleistocene sea-level lowstands (???2.8 and 1.75 m.y. B.P.) and subsequently truncated and offset to the northwest. There have also been a minimum of two canyon-cutting episodes within the past 750,000 years, after the entire Ascension Canyon system migrated to the northwest past Monterey Canyon. We attribute these late Pleistocene erosional events to relative lowstands of sea level 750,000 and 18,000 yrs B.P. The late Pleistocene and Holocene evolution of the six southeastern heads also appears to have been controlled by structural uplift of the Ascension-Monterey basement high at the southeastern terminus of the Outer Santa Cruz Basin. We believe that uplift of this basement high sufficiently oversteepened submarine slopes to induce gravitational instability and generate mass movements that resulted in the erosion of the canyon heads. Most significantly, though, our results and interpretations support previous proposals that submarine canyons along strike-slip continental margins can originate by tectonic trunction and lateral offset. ?? 1986.

Nagel, D.K.; Mullins, H.T.; Greene, H. Gary

1986-01-01

41

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

Microsoft Academic Search

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

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

2007-01-01

42

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

43

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

NASA Astrophysics Data System (ADS)

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

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

2012-11-01

44

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 bathymetry regression power law landslide Submarine canyons are common features of continental margins. Though it is known that submarine canyons form pri- marily from erosion induced by submarine sediment

ten Brink, Uri S.

45

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

NASA Astrophysics Data System (ADS)

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

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

2012-06-01

46

Delaware River: Evidence for its former extension to Wilmington Submarine Canyon  

USGS Publications Warehouse

Seismic-reflection profiles indicate that during the Pleistocene the Delaware River flowed across the continental shelf east of Delaware Bay and emptied into Wilmington Submarine Canyon. The ancestral valley (width, 3 to 8 kilometers; relief, 10 to 30 meters) is buried, is not reflected in the surface topography, and probably predates the formation of the present canyon head.

Twichell, D.C.; Knebel, H. J.; Folger, D.W.

1977-01-01

47

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

NASA Astrophysics Data System (ADS)

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

Jobe, Z.

2010-12-01

48

Recent sea beam mapping of Ascension-Monterey Submarine Canyon System  

SciTech Connect

Extensive Sea Beam and Bathymetric Swatch Survey System (BS{sup 3}) data covering the Ascension-Monterey Submarine Canyon system and adjoining areas and canyons were collected offshore central California. Many discovered geomorphological features lead to significant new geologic conclusions about the formation and processes of submarine canyons in general and disclose unique sedimentary and tectonic features of the Ascension-Monterey Canyon system. The highly detailed bathymetric maps constructed from the Sea Beam data indicate that the seafloor topographic pattern is influenced by sedimentary and tectonic processes; both remain active along the central California margin. Interpretations of MOAA composite maps, final raw Sea Beam bathymetric maps, and three-dimensional physiographic renditions from bathymetric data indicate a diverse and complex geomorphology for the Ascension-Monterey Submarine Canyon system and adjoining region. Five distinct geomorphologic provinces and four well-defined geographic areas are mapped. Canyons cut by faults and canyon walls actively undergoing mass wasting are prominently displayed in the Sea Beam data. Sedimentary processes illustrating canyon channel capture and the formation of extensive mega-sedimentary wave fields where the canyons debouch onto the abyssal plain are spectacularly well defined. This new tool of seafloor mapping is contributing significant data for the geological interpretation of continental margins and seafloor in the world's oceans.

Greene, H.G. (Geological Survey, Menlo Park, CA (USA))

1990-06-01

49

Morpho-sedimentary features and sediment dispersal of the Fangliao Submarine Canyon in the active margin offshore SW Taiwan  

Microsoft Academic Search

Using newly collected multi-channel seismic profiles and bathymetric data this paper characterizes morphology and relates it to structural and sedimentary processes in the Fangliao Submarine Canyon and contrasts with the nearby Kaoping Canyon about 20 km in distance by the sediment dispersal in terms of source to sink. The Fangliao Canyon consists of three distinct morphologic parts: an upper canyon,

Y. H. Chang; C. S. Chiang; H. S. Yu

2009-01-01

50

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

51

Rapid changes in the head of the Rio Balsas Submarine Canyon system, Mexico  

USGS Publications Warehouse

The investigation of a river delta and the heads of several nearby submarine canyons in western Mexico produced evidence for rapid changes in the configuration and depth of the nearshore portions of canyon tributaries. General scarcity of data on the rates of submarine canyon formation and the relationship to river discharge should make these results of special interest. The Rio Balsas, one of Mexico's largest rivers, empties into the ocean near the heads of a large submarine canyon that terminates in the Middle America Trench. One of the distributaries of the Rio Balsas presently is discharging at the head of Can??o??n de la Necesidad, which is being eroded actively. Two inactive canyons are related to former discharge channels of the river. Their heads lie at some distance from shore and are being filled with sediment. The Can??o??n de Petacalco, not now receiving sediment directly from a Rio Balsas distributary, has remained active because the shoreline has not retreated far. Until about 100 years ago its head was being filled with fine-grained and highly organic sediments from a nearby rivermouth, while the coarse portion of the sediment supply joined the canyon via a tributary farther seaward. Since then the river has shifted away from this canyon, and the horizontally stratified sediments in the canyon head have been incised as much as 20-30 m, as evidenced by three 14C dates of organic material exposed in the steep to overhanging canyon walls. The changes in the shallow portion of the Rio Balsas submarine canyons seem to be related to changes in river discharge pattern, either directly or indirectly. A shifting point source of sediment supply either activates a pre-existing, partly filled canyon, or erodes a new one near the new river mouth, whereas the canyon at the abandoned river mouth is deactivated following retreat of the shoreline. The heads of the different tributaries form a dendritic pattern in Holocene unconsolidated sediment. Subaerial processes are not involved in the formation of these submarine canyons. Thus, a dendritic pattern of submarine canyons is not necessarily indicative of subaerial erosion. ?? 1970.

Reimnitz, E.; Gutierrez-Estrada, M.

1970-01-01

52

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

53

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

54

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

55

Geomorphic process fingerprints in submarine canyons1 Daniel S. Brothers*, Uri S. ten Brink, Brian D. Andrews, Jason D. Chaytor, David C.2  

E-print Network

1 Geomorphic process fingerprints in submarine canyons1 Daniel S. Brothers*, Uri S. ten *Corresponding author: dbrothers@usgs.gov; 508-457-229310 11 Abstract12 Submarine canyons are common from the continents to the deep sea.14 Though it is known that submarine canyons form primarily from

ten Brink, Uri S.

56

Clast-contact conglomerates in submarine canyons: possible subaqueous sieve deposits  

SciTech Connect

Thick, coarse, clast-contact conglomerates in submarine canyon fill have previously been attributed to rock-fall, grain-flow, or winnowing processes. However, these processes do not adequately explain some thick conglomeratic sequences. The proposed process of subaqueous sieve deposition could account for these clast-contact conglomerates. Subaerial sieve deposition has been documented on small-scale fan models and on alluvial fans. A subaerial sieve deposit begins as a debris flow which at some point freezes up. The matrix is then lost by subsequent filtration or outflow, and the emplacement of a clast-contact gravel ensues. A subaqueous sieve deposit would be slightly modified in that the matrix would not be lost by filtration into the submarine canyon floor, but rather by outflow at the terminus of the lobe immediately after deposition, or possibly from the top and/or sides of the freezing flow mass during transport. Besides forming in submarine canyons, subaqueous sieve deposits might also occur in paralic, submarine fan channel, and base-of-the-slope settings. In substantiating the existence of subaqueous sieve deposits, the sedimentary structures and grain-size data from recent sieve deposits on alluvial fans are compared to those of ancient submarine canyon deposits. Numerous similarities are found supporting this new method of deposition. Some discrepancies are encountered, but these are expected due to modifications caused by an aqueous medium.

Fitzgerald, M.S.

1987-05-01

57

Internal wave behaviour in the submarine canyons of the Celtic Sea Shelf  

NASA Astrophysics Data System (ADS)

The Celtic Sea, located off the south coast of Ireland, is a 100-200m deep shelf sea that is notable for the presence of large tidal currents and strong seasonal fluctuations in surface heating and cooling. The shelf edge is a region of rough topography and barotropic tidal flows generate internal waves and associated baroclinic energy fluxes. These internal tides are reflected if they encounter topographic features. The reflection is dependent on the relative topographic slope and can be subcritical (waves continue to shoal), supercritical (waves are reflected back into deep water) or critical (nonlinear effects, potential wave breaking and turbulent mixing). Submarine canyons are a common bathymetric feature along the Celtic Sea shelf edge and are known to trap and focus internal waves towards the head of the canyon, leading to high levels of turbulent mixing. This mixing may drive vertical nutrient fluxes and enhance primary productivity at the shelf edge. Celtic Sea submarine canyons are typically dendritic and vary in cross sectional profile along the length of their axis, providing many different topographic slope values. Using a numerical model, I will investigate the propagation of internal waves through both idealised canyons and realistic canyon bathymetry from the Celtic Sea shelf edge. Using the results I will attempt to parameterise submarine canyon morphology based on its effect on the internal wave field.

Aslam, Tahmeena; Hall, Rob; Heywood, Karen; Dye, Stephen

2014-05-01

58

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

59

Marine Protected Area Design and the Spatial and Temporal Distribution of Cetaceans in a Submarine Canyon  

Microsoft Academic Search

The Gully, the largest submarine canyon off the coast of eastern Canada, is currently under consid- eration as a marine conservation area, primarily because of the increasing interest in oil and gas production on the Scotian Shelf. Cetaceans, as a guild of abundant, large organisms that are relatively sensitive to such threats, provide a reliable means to determine the boundaries

Sascha K. Hooker; Hal Whitehead; Shannon Gowans

1999-01-01

60

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

Microsoft Academic Search

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

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

1984-01-01

61

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

62

Event-driven sediment flux in Hueneme and Mugu submarine canyons, southern California  

USGS Publications Warehouse

Vertical sediment fluxes and their dominant controlling processes in Hueneme and Mugu submarine canyons off south-central California were assessed using data from sediment traps and current meters on two moorings that were deployed for 6 months during the winter of 2007. The maxima of total particulate flux, which reached as high as 300+ g/m2/day in Hueneme Canyon, were recorded during winter storm events when high waves and river floods often coincided. During these winter storms, wave-induced resuspension of shelf sediment was a major source for the elevated sediment fluxes. Canyon rim morphology, rather than physical proximity to an adjacent river mouth, appeared to control the magnitude of sediment fluxes in these two submarine canyon systems. Episodic turbidity currents and internal bores enhanced sediment fluxes, particularly in the lower sediment traps positioned 30 m above the canyon floor. Lower excess 210Pb activities measured in the sediment samples collected during periods of peak total particulate flux further substantiate that reworked shelf-, rather than newly introduced river-borne, sediments supply most of the material entering these canyons during storms.

Xu, J.P.; Swarzenski, P.W.; Noble, M.; Li, A.-C.

2010-01-01

63

Submarine canyons as the preferred habitat for wood-boring species of Xylophaga (Mollusca, Bivalvia)  

NASA Astrophysics Data System (ADS)

Submarine canyons are often viewed as natural “debris concentrators” on the seafloor. Organic substrates may be more abundant inside than outside canyon walls. To determine the effects of the presence these substrates in the Blanes submarine canyon (NW Mediterranean) and its adjacent western open slope, we deployed wood to study colonizing organisms. Three replicate pine and oak cubes (i.e. most common trees inland) were moored at 900, 1200, 1500 and 1800 m depth and collected after 3, 9 and 12 months. Wood from inside the canyon was significantly more heavily colonized by the five morphotypes of wood-boring bivalves than was wood on the adjacent open slope. Xylophaga sp. A dominated all wood types and locations, with peak abundance at 900 and 1200 m depth. Its growth rate was highest (0.070 mm d-1) during the first three months and was faster (or it recruits earlier) in pine than in oak. Size distribution showed that several recruitment events may have occurred from summer to winter. Xylophaga sp. B, appeared first after 9 months and clearly preferred pine over oak. As the immersion time was the same, this strongly supported a specific association between recruiters and type of substrate. Three morphotypes, pooled as Xylophaga spp. C, were rare and seemed to colonize preferentially oak inside the canyon and pine in the adjacent open slope. Individuals of Xylophaga were more abundant inside the canyon than in nearby off-canyon locations. Blanes Canyon may serve as a long-term concentrator of land-derived vegetal fragments and as a consequence sustain more animals. Are the species richness and abundance of wood-boring bivalves higher inside the canyon than on the adjacent open slope? Do the composition and density of the wood-boring bivalves change with deployment time and depth, as well as on the type of the sunken wood? What is the growth rate of the dominant wood-boring species?

Romano, C.; Voight, J. R.; Company, J. B.; Plyuscheva, M.; Martin, D.

2013-11-01

64

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

SciTech Connect

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

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

1988-08-01

65

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

66

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

67

Sedimentologic evolution of a submarine canyon in a forearc basin, Upper Cretaceous Rosario Formation, San Carlos, Mexico  

SciTech Connect

The walls, floor, and fill of a submarine canyon are well-exposed near San Carlos, Mexico, in forecarc strata of the Upper Cretaceous Rosario Formation. The submarine canyon is about 7 km wide and at least 230 m deep and has eroded a minimum of 150 m into underlying fluvial red beds. It is unclear whether subaerial or submarine processes initiated the canyon cutting; however, marine processes, especially debris flows, modified the morphology of the submarine canyon. The submarine canyon fill and overlying slope deposits form two major fining-upward sequences. The first includes a 120 m thick lower conglomerate-sandstone unit (LCSU) at the base of the canyon fill overlain by a 50-110 m thick middle mudstone-sandstone unit (MMSU). The MMSU consists predominantly of mudstone and thin-bedded sandstone, but includes a channel filled with sandstone beds that form a fining- and thinning-upward sequence. This sequence is overlain by the second major sequence, a 0-60 m thick upper conglomerate-sandstone unit (UCSU), which is confined to three channels within the submarine canyon and passes gradationally upward into slope mudstone. Each of the two major fining-upward sequences records a gradual decrease in supply of coarse-grained sediment to the submarine canyon head. The first fining-upward sequence may correspond to a lowstand and subsequent rise in global sea level or, alternatively, may have resulted from local downdropping of the basin. The second fining-upward sequence does not correspond to global sea level fluctuations but is age-correlative with a drop then rise in relative sea level recognized by other workers 300-400 km to the north in the San Diego-Ensenada area. This sea level drop is inferred to have been a regional-scale tectonic event that affect the forearc basin along its length. 18 figures, 2 tables.

Morris, W.R.; Busby-Spera, C.J.

1988-06-01

68

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

69

Submarine canyon in a forearc basin, Upper Cretaceous Rosario Group, Baja California, Mexico  

SciTech Connect

Late Cretaceous marine and nonmarine sedimentary rocks of the Rosario Group, deposited in one or more forearc basins, are exposed discontinuously from San Diego to Punta Canoas. Near the southern end of this belt, at San Carlos, mexico, a well-exposed, 6-km wide submarine canyon cuts at least 150 m into a fluvial section. Paleocurrent data indicate a west-southwest-directed sediment transport in the canyon. Large blocks of limestone 3-4 m in size, derived from the Early Cretaceous arc basement complex of the Alisitos group, were transported at least 20 km from the source area in the submarine canyon. The canyon fill consists of a basal and upper conglomerate to sandstone unit separated by a 20 to 45-m thick shale and sandstone unit, and capped by a second shale and sandstone unit of unknown thickness. The lower conglomerate-sandstone unit ranges from 20 to 140 m thick, and cuts into fluvial deposits in a curved or steplike pattern. The upper conglomerate-sandstone unit fills deep channels incised into a sandstone-shale unit and is 35-60 m thick. The conglomerates represent high-density turbidites and debris flows. Sandstones are massive (ungraded or graded), or display Bouma AB or ABC divisions. Shaly slump blocks, derived from channel margins or terraces, were injected by clastic sills and dikes as they were incorporated into the conglomeratic flows. Slump blocks increase in frequency and size near the northern canyon wall. This pattern has been attributed to a meandering channel with slumping on the outer bend of a meander. The abrupt contact between the conglomerate-sandstone units and the overlying shale-sandstone units indicates that on two occasions the canyon head was abruptly denied access to sources of coarse-grained material. This cyclic pattern may be the result of tectonic events or eustatic sea level changes.

Morris, W.R.; Busby-Spera, C.J.; Boles, J.R.

1986-04-01

70

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

USGS Publications Warehouse

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

Laursen, J.; Normark, W.R.

2002-01-01

71

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 S.; Chaytor, Jason D.; ten Brink, Uri S.; Ross, Steve W.; Brooke, Sandra

2013-01-01

72

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

73

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

74

Spatial distribution of phytoplankton assemblages in the Nazaré submarine canyon region (Portugal): HPLC-CHEMTAX approach  

NASA Astrophysics Data System (ADS)

The distribution and composition of phytoplankton assemblages were studied in the Nazaré submarine canyon, during an upwelling event, using high-performance liquid chromatography (HPLC) pigment analysis, complemented by microscopic qualitative observations. High chlorophyll a (Chl a) concentrations were recorded in the canyon head, near the coast, where values greater than 4 ?g L - 1 were observed. In contrast, Chl a was relatively low in offshore regions, with values below 0.5 ?g L - 1 . The most abundant accessory pigments were fucoxanthin, peridinin, diadinoxanthin and 19'-hexanoyloxyfucoxanthin. Pigment data information was analyzed using the CHEMTAX software to estimate the contribution of different taxonomic groups to total Chl a. North of the canyon head, an area with high concentration of peridinin-containing dinoflagellates was identified (with presence of chain-forming toxic dinoflagellates). The presence of these organisms was associated with mixed water columns and phosphate values lower than the ones south of the canyon head, where a dominance of diatoms was recorded. The rest of the study region showed a dominance of prymnesiophytes and a significant contribution of cyanobacteria at oceanic stations. This study demonstrates the usefulness of using pigment analysis to study spatial distribution of phytoplankton groups in relation to a complex physical environment.

Mendes, Carlos Rafael; Sá, Carolina; Vitorino, João; Borges, Carlos; Tavano Garcia, Virginia Maria; Brotas, Vanda

2011-07-01

75

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

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

76

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

77

Nonlinear seismic response of tall concrete-faced rockfill dams in narrow canyons  

Microsoft Academic Search

The seismic behavior of tall concrete face rockfill dams in narrow canyons is investigated, based on numerical simulation of the staged construction, creep settlements, reservoir impoundment and seismic shaking of the dam. The study takes into account the flexibility of the canyon rock, the hydrodynamic effects and potential dynamic rockfill settlements. The static analysis uses a hyperbolic model for the

Panos Dakoulas

78

Crescent?shaped slab slides in a submarine canyon system, Arequipa fore?arc basin, off southern Peru  

Microsoft Academic Search

SeaMARC II side?scan imagery and bathymetry, seismic reflection, and free?fall core sampling data reveal the morphology, structure, and hydrology controls on the formation and development of a series of crescent?shaped slab slides along the submarine canyon walls in the Arequipa fore?arc basin off southern Peru. The crescent?shaped slab slides occur in a segment of an approximately 25?km?long canyon course and

Chang Li

1993-01-01

79

The surface sediment distribution and sedimentary environment of the Pearl River Submarine Canyon  

NASA Astrophysics Data System (ADS)

The grain size composition, particle size parameters, clay mineral, and detrital mineral of surface sediment of this The Pearl River Submarine Canyon (the PRSC, for short) area have been measured and analyzed, which were took sampling in 2005 and 2006 in the northern South China Sea. The results show that the isolines distribution features of these parameters have very good corresponding relation with the geomorphology of the PRSC. On the continental-shelf slope break of the PRSC head (123m-1500m water depth), the close interval isolines of the surface sediment particle size percentage content and size parameters nearly parallel with the water depth isolines. The data of sand percentage content and mean grain size, sorting coefficient and skewness decreases with the increase of water depth. The other way around, the silt and clay percentage content and kurtosis value increase with deeper water. These show that in the canyon head sediment distribution was controlled by the material source (mainly comes from the Pearl River), slope and the northern South China Sea offshore current. In the main PRSC area, the surface sediment grain size composition content and grain size parameter numerical isolines have become a isoline platform which has the similar shape with the main PRSC and extended to the northeast and southwest deep sea basin. This means that the sedimentary environment of main canyon is apparently different with the head environment, that is affected by the high-temperature and high-salt the South China Sea Branch of by the Kuroshio along the 3500 m water depth isoline and alone the canyon to bending. The 25% percentage content isoline of the calcium biological and 45% percentage content isoline of the light mineral show a broadband distribution along the head and upside of the PRSC, and reduces in the entrance with the water depth isolines, apparently influenced by the South China Sea Branch of the Kuroshio. A high value area of the silt, clay mineral, light mineral, heavy mineral, silicon biological, and calcium biological appears to the entrance of the PRSC, which may be controlled by a perennial anticlockwise current. But how the materials passed through the South China Sea Branch of the Kuroshio and sediment here still is not be solved. The distribution of clay minerals close to the distribution of grain size, around the main canyon with more loose and uniform interval value isolines. It is lower of the percentage content isolines value of the Illite, Kaolinite and Chlorite in the canyon than the values around the canyon (specially at northeast, northwest, southwest ). And the Smectite percentage content has the opposite distribution, the value is higher in the canyon than out the canyon. Which means that the Traditional knowledge about ocean clay minerals distribution is influenced by the latitude is not adaptive at submarine canyon area. To sum up, the existence of the PRSC has changed the material transport mode from land to deep ocean basin in the northern South China Sea. Not only it played a transfer passageway, but also it played the role of the sorting and aggregation, which is beneficial to the formation and gathering of certain minerals. This work were supported by the NSFC (41106046), the Youth Ocean Science Fund Project, SOA(2011333) and the Basic Scientific Researching Specific Funds of SIO, SOA (JT1002)

Han, X.; Chu, F.; Li, J.; Xu, D.; Zhang, W.

2012-12-01

80

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

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

81

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

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

82

Different types of sediment gravity flows detected in the Var submarine canyon (northwestern Mediterranean Sea)  

NASA Astrophysics Data System (ADS)

Current velocities and vertical sediment fluxes in the Var submarine canyon were assessed at three stations respectively at 800 m, 1200 m and 1800 m depth, using moorings deployed for 4 months during winter 2008-2009. During this period, we observed three major sediment gravity flows, all characterized by sudden increases in current velocity that lasted 2-5 h and by downward particle fluxes. Each gravity flow, described using a high frequency current meter and two Acoustic Doppler Current Profiler (75 and 300 kHz ADCP) showed distinctive features. The first event, triggered during a flood of the Var River, was determined to be a hyperpycnal current with a large vertical extent (>100 m high) and relatively low velocity (40 cm s-1). The second event, observed after a Var River flood, was more energetic with a maximum horizontal current peak of 60 cm s-1 but with a low vertical extent (30 m high). This event was considered to be a turbidity landslide. The third was the result of a local canyon wall failure. It was characterized by a speed of >85 cm s-1. These peaks of current speed were associated with large clouds of material that transported sediment along the canyon and reached up to 200 g m-2 d-1 of sediment (>1 g m-2 d-1 of organic carbon). Our measurements in the Var canyon show the important role of gravity flows transporting particulate matter to the deep-sea floor. These large inputs of sediment and organic carbon may have a significant impact on deep-sea carbon storage in the Mediterranean Sea.

Khripounoff, A.; Crassous, P.; Lo Bue, N.; Dennielou, B.; Silva Jacinto, R.

2012-11-01

83

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

84

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

85

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

86

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

87

Analysis of Submarine Landslides and Canyons along the U.S. Atlantic Margin Using Extended Continental Shelf Mapping Data  

NASA Astrophysics Data System (ADS)

U.S. Geological Survey (USGS) studies of the U.S. Atlantic continental slope and rise aim to understand the: 1) the role of submarine landslides in tsunami generation, and 2) the linkages between margin morphology and sedimentary processes, particularly in and around submarine canyon systems. Data from U.S. Extended Continental Shelf (ECS) and numerous subsequent mapping surveys have facilitated the identification and characterization of submarine landslides and related features in fine detail over an unprecedented spatial extent. Ongoing analysis of USGS collected piston cores, sub-bottom and multichannel seismic (MCS) reflection profiles, and an extensive suite of legacy MCS data from two landslides, the Southern New England landslide zone and the Currituck Landslide, suggest that the most recent major landslide events are pre-Holocene, but that failures were complex and most likely multi-phase, at times resulting in extensive overlapping debris deposits. Piston core records plus visual observations of the seafloor from recent TowCam deployments and NOAA Ship Okeanos Explorer ROV dives reveal ongoing development of colluvial wedge-style debris aprons at the base of scarps within these landslides, showing that these regions continue to evolve long after the initial failure events. Multibeam bathymetry data and MCS profiles along the upper slope reveal evidence for vertical fluid migration and possible seabed gas expulsion. These observations underscore the need to reevaluate the sources of pore fluid overpressure in slope sediments and their role in landslide generation. ECS and more recent multibeam mapping have provided the opportunity to investigate the full extent of submarine canyon morphology and evolution from Cape Hatteras up to the US-Canadian EEZ, which has led to better understanding of the important role of antecedent margin physiography on their development. Six submarine canyon systems along the margin (Veatch, Hydrographer, Hudson, Wilmington-Baltimore, Norfolk-Washington, and Hatteras) are being investigated from the canyon heads down to their deep-water submarine fans in an effort to characterize their sediment transport history and constrain the influences of external processes on their morphology. Each canyon-fan system is morphologically unique and is strongly controlled by source region, antecedent margin morphology, landslide and debris flow processes, and the long-term influence of deep-water (along-slope) currents.

Chaytor, J. D.; Brothers, D. S.; Ten Brink, U. S.; Hoy, S. K.; Baxter, C.; Andrews, B.

2013-12-01

88

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

Microsoft Academic Search

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

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

2006-01-01

89

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

90

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

Microsoft Academic Search

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

Andrew Green

2011-01-01

91

Microbial communities in sunken wood are structured by wood-boring bivalves and location in a submarine canyon.  

PubMed

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

92

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

93

Spatial scale-dependent habitat heterogeneity influences submarine canyon macrofaunal abundance and diversity off the Main and Northwest Hawaiian Islands  

NASA Astrophysics Data System (ADS)

The mapping of biodiversity on continental margins on landscape scales is highly relevant to marine spatial planning and conservation. Submarine canyons are widespread topographic features on continental and island margins that enhance benthic biomass across a range of oceanic provinces and productivity regimes. However, it remains unclear whether canyons enhance faunal biodiversity on landscape scales relevant to marine protected area (MPA) design. Furthermore, it is not known which physical attributes and heterogeneity metrics can provide good surrogates for large-scale mapping of canyon benthic biodiversity. To test mechanistic hypotheses evaluating the role of different canyon-landscape attributes in enhancing benthic biodiversity at different spatial scales we conducted 34 submersible dives in six submarine canyons and nearby slopes in the Hawaiian archipelago, sampling infaunal macrobenthos in a depth-stratified sampling design. We employed multivariate multiple regression models to evaluate sediment and topographic heterogeneity, canyon transverse profiles, and overall water mass variability as potential drivers of macrobenthic community structure and species richness. We find that variables related to habitat heterogeneity at medium (0.13 km2) and large (15-33 km2) spatial scales such as slope, backscatter reflectivity and canyon transverse profiles are often good predictors of macrobenthic biodiversity, explaining 16-30% of the variance. Particulate organic carbon (POC) flux and distance from shore are also important variables, implicating food supply as a major predictor of canyon biodiversity. Canyons off the high Main Hawaiian Islands (Oahu and Moloka'i) are significantly affected by organic enrichment, showing enhanced infaunal macrobenthos abundance, whereas this effect is imperceptible around the low Northwest Hawaiian Islands (Nihoa and Maro Reef). Variable canyon alpha-diversity and high rates of species turnover (beta-diversity), particularly for polychaetes, suggest that canyons play important roles in maintaining high levels of regional biodiversity in the extremely oligotrophic system of the North Pacific Subtropical Gyre. This information is of key importance to the process of MPA design, suggesting that canyon habitats be explicitly included in marine spatial planning. The low-islands of Nihoa and Maro Reef in the NWHI showed a lack of sustained input of terrestrial and macrolagae detritus, likely having an influence on the observed low macrofaunal abundances (see further discussion of ‘canyon effects’ in Section 4.3), and showing the fundamental role of coastal landscape characteristics in determining the amount and nature of allochthonous organic matter entering the system. Total and highly-mobile invertebrate megafauna abundances were two to three times higher in the submarine canyons and slopes of the MHI contrasted with the NWHI (Vetter et al., 2010), also demonstrating the role of this larger contribution of terrestrial and coastal organic enrichment in the MHI contrasted with the NWHI.

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

2014-06-01

94

A delta-fed submarine ramp alternative to the canyon-fed depositional model of the Stevens submarine fan system, southeastern San Joaquin basin, Kern County, California  

SciTech Connect

Deep-marine sands of the Upper Miocene Stevens Sandstone, one of the most important hydrocarbon-producing units in the United States, were deposited by sediment-gravity flows in the Bakersfield Arch area of the southern San Joaquin basin. The Stevens Sandstone has historically been considered to be a thick turbidite succession shed off the southern Sierra Nevada as four fans in a long-lived submarine fan system fed by several large submarine canyons. Access to previously unavailable proprietary 2-D and 3-D seismic data sets, carefully calibrated by well-log and core data, permits a more complete understanding of the depositional architecture of this highly petroliferous, deep-marine depositional system. This study concludes that these units were deposited in a delta-fed, line- sourced deep-sea system, whose distribution was structurally-controlled. Seismic lines examined in this study show evidence for a large fault-controlled slump feature in the area that has been referred to as {open_quotes}Rosedale Canyon,{close_quotes} and no evidence supports the existence of submarine canyons feeding the system. The highly progradational Stevens interval consists of thick siliciclastic units separated by thin, intervening biosiliceous shales. Seismically, the upper bounding surfaces of these biosiliceous shales represent major downlap surfaces. As sands were deposited by high-density turbidity currents, the area of the present Bakersfield Arch developed into a deep-sea braid plain. Smaller-scale linear features detected on horizon slices through the 3-D seismic data cube have been interpreted in this study as braided channelform features deposited on the deep-sea braid plain. Hydrocarbon production along these linear trends may be associated with porosity and permeability variations resulting from channelized versus non-channelized sedimentation.

Harrison, C.P. [Amoco Production Co., Houston, TX (United States)

1996-12-31

95

A delta-fed submarine ramp alternative to the canyon-fed depositional model of the Stevens submarine fan system, southeastern San Joaquin basin, Kern County, California  

SciTech Connect

Deep-marine sands of the Upper Miocene Stevens Sandstone, one of the most important hydrocarbon-producing units in the United States, were deposited by sediment-gravity flows in the Bakersfield Arch area of the southern San Joaquin basin. The Stevens Sandstone has historically been considered to be a thick turbidite succession shed off the southern Sierra Nevada as four fans in a long-lived submarine fan system fed by several large submarine canyons. Access to previously unavailable proprietary 2-D and 3-D seismic data sets, carefully calibrated by well-log and core data, permits a more complete understanding of the depositional architecture of this highly petroliferous, deep-marine depositional system. This study concludes that these units were deposited in a delta-fed, line- sourced deep-sea system, whose distribution was structurally-controlled. Seismic lines examined in this study show evidence for a large fault-controlled slump feature in the area that has been referred to as [open quotes]Rosedale Canyon,[close quotes] and no evidence supports the existence of submarine canyons feeding the system. The highly progradational Stevens interval consists of thick siliciclastic units separated by thin, intervening biosiliceous shales. Seismically, the upper bounding surfaces of these biosiliceous shales represent major downlap surfaces. As sands were deposited by high-density turbidity currents, the area of the present Bakersfield Arch developed into a deep-sea braid plain. Smaller-scale linear features detected on horizon slices through the 3-D seismic data cube have been interpreted in this study as braided channelform features deposited on the deep-sea braid plain. Hydrocarbon production along these linear trends may be associated with porosity and permeability variations resulting from channelized versus non-channelized sedimentation.

Harrison, C.P. (Amoco Production Co., Houston, TX (United States))

1996-01-01

96

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

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

97

Limited depth zonation among bathyal epibenthic megafauna of the Gully submarine canyon, northwest Atlantic  

NASA Astrophysics Data System (ADS)

The Gully is a large submarine canyon incised into the Scotian Shelf, in the northwest Atlantic. A submersible-mounted camera was used to collect 17 km of high resolution video imagery of the soft sediment flanks and floor of the canyon between 1000 and 2500 m depth. A depth-stratified random survey design with two transects per stratum was followed. Depth strata were drawn at 1000-1500 m, 1500-2000 m and 2000-2500 m reflecting global and regional faunal boundaries. The 47,614 individuals or colonies observed on the transects were identified into 49 unique taxa drawn from 7 phyla, while 21 additional taxa were observed between the transect lines. Cnidaria was the most diverse phylum (22 taxa) on the transects, followed by the Echinodermata (15 taxa). Most fauna were sessile or sedentary suspension feeders. A species of Xenophyophorida, likely Syringammina sp., was the most abundant taxon. Cluster analysis of transects based on a Bray-Curtis (BC) matrix of species abundance identified one cluster of five transects and one independent transect - the deepest transect (2406 m average depth). A similarity profile test indicated that this structure is not random. There was a significant change in the megafaunal assemblage with depth over scales of 10s of kilometers, accounting for 65% of the variation in the BC matrix. Both total organic carbon and labile carbon were higher in cores from the 1000-1500 m stratum than at greater depth, consistent with transport of food and sediments into the canyon from shallower waters. The first principal component calculated from species abundances separated the two transects from the 1000-1500 m depth stratum from the others indicating that sediment food supply influences community structure and composition. Over small spatial scales (?10 m), eight groups of species associations were identified. However, the associations between the species within each group were not strong with the highest correlation between the Xenophyophorida and the Pennatulacea (?=0.66). At this spatial scale substrate type was an important factor, with hard and soft bottom species associations being identified.

Kenchington, E. L.; Cogswell, A. T.; MacIsaac, K. G.; Beazley, L.; Law, B. A.; Kenchington, T. J.

2014-06-01

98

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

NASA Astrophysics Data System (ADS)

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 to better constrain the contemporary sediment transport processes in this region. A network of mooring lines equipped with current meters and turbidity sensors at 5 m above bottom were deployed between 300 m and 1900 m depth along the axes of the two Lacaze-Duthiers and Cap de Creus neighbor canyons, as well as across the southern open slope from October 2005 to October 2006. Recorded data indicate that dense shelf water cascading was the main shelf-to-slope sediment transport process in the area, acting from January to April-May 2006. The dense water and sediment transport was not only through submarine canyons, but also along the southern open slope. The most important suspended sediment transport event was due to the intense cascading pulse occurring in January 2006, which produced a strong sediment flux increase along the Cap de Creus Canyon down to 1900 m depth and also along the open slope at 1000 m depth. A significant sediment flux increase also occurred in March-April 2006 due to another intense cascading pulse. In this transport event, suspended sediment concentration only increased at 1000 m depth in the Cap de Creus Canyon and on the open slope, but not at the canyon head, suggesting a redistribution of sediments previously deposited at mid-canyon depths. Deeper than 1000 m, net fluxes show that most of the suspended sediment left the canyon and flowed along the southern open slope towards the Catalan margin, whereas a small part flowed downcanyon and was exported basinward through the canyon mouth. Additionally, the increase of the deep-sea near-bottom currents induced by open-sea convection processes, combined with the arrival of deep cascading pulses, also generated moderate but continuous suspended sediment transport at deeper slope regions.

Palanques, Albert; Puig, Pere; Durrieu de Madron, Xavier; Sanchez-Vidal, Anna; Calafat, Antoni; Pascual, Catalina; Heussner, Serge; Canals, Miquel

2010-05-01

99

A western thalweg of the Princeton Valley submarine canyon system as a reservoir and a trap near Willows, California  

SciTech Connect

The Princeton Valley submarine canyon system has long been an important reservoir and trapping mechanism in the northern Sacramento Valley, California. Recently a western thalweg of the system, identified north of Willows, California, has proven to be a significant trapping mechanism for gas in truncated Kione Formation sandstones. Both Upper Cretaceous Kione Formation and Paleocene Princeton Valley sandstones are exploratory objectives in the area and are productive in existing wells. The Kione Formation, a sand-rich deltaic sequence approximately 2,000 ft thick, has been truncated to the west by the Princeton Valley submarine canyon system. The canyon (gorge) has been subsequently filed with primarily impermeable shales, providing a trap for migrating gases in the truncated sands. The trend was discovered in 1977 by Shell Oil Company based on seismic and was the first substantiated evidence of a western thalweg of the Princeton Gorge in the Willows area. To date, four wells have been completed along the trend and current exploratory efforts are attempting to follow the gorge trend.

Blake, R.G. (Fleet Oil Co., Irvine, CA (USA)); Bainer, R.W.

1990-05-01

100

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

Microsoft Academic Search

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

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

2008-01-01

101

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

102

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

103

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

NASA Astrophysics Data System (ADS)

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

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

2005-12-01

104

Submarine canyons of north-western Sicily (Southern Tyrrhenian Sea): Variability in morphology, sedimentary processes and evolution on a tectonically active margin  

NASA Astrophysics Data System (ADS)

Swath-bathymetry, mono-channel and multi-channel seismic reflection records acquired during the last two decades on the northern Sicilian margin have unveiled a dense network of submarine canyons within the depth range of 80-2100 m. The canyons display a relevant variability in their geometry, morphology and sedimentary processes. The margin shows a young, tectonically active shelf to slope setting, linking the Sicilian-Maghrebian Thrust Belt to the Tyrrhenian oceanic realm, developed during the Neogene-Quaternary time span. The aim of this study is to highlight the main governing factors that contributed to the evolution and differentiation of the northern Sicilian canyons, mainly focusing on the Gulf of Palermo and on the Gulf of Castellammare. Tectonic control is more evident in the canyons of the Gulf of Palermo, with submarine landslides retrograding on a steep slope and mainly controlling their evolution. Otherwise, canyons, tributaries and gullies mapped in the Gulf of Castellammare developed on a less steep substrate and display sinuous to meandering paths, with a relevant role of coastal/shelf sedimentary inputs and downslope turbidity processes in their formation. Results suggest that, despite the geographically close proximity of the two study areas, the different structural settings of the Castellammare and Palermo Basins are mainly responsible for canyon variability. Data indicate likely on-going uplift and tilting movements along the Sicilian margin, influencing the development of the studied canyons, which have probably been more active during the Quaternary glacial maxima than they are in the present day.

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

2014-06-01

105

Submarine canyon formation and evolution in the Argentine Continental Margin between 44°30'S and 48°S  

NASA Astrophysics Data System (ADS)

In the framework of the Vulnerable Marine Ecosystems (VME) of the High Seas of the South West Atlantic, large areas of the Argentine Continental Margin (ACM) between 44°30'S and 48°S have been swath-mapped for the first time, obtaining full data coverage of the seafloor in this region between the outermost continental shelf and the middle slope down to 1600 m water depth. The slope is characterized by the presence of smooth terraces (Nagera, Perito Moreno and Piedra Buena) that widen towards the south, limited by morphological steps with evident signs of erosion in the form of scours. These terraces form part of the Argentine contourite depositional systems, generated by the interaction of the northwards flowing Antarctic water masses with the seafloor. Within the studied area, seven canyons and their multiple branches dissect the upper and middle continental slopes, from west to east, across the terraces and the steps. These canyons, which belong to the Patagonia submarine canyon system and are collected at a depth of ~ 3.5 km by a slope-parallel, SSW-NNE-oriented channel known as the Almirante Brown transverse canyon, display a large variety of morphologies. These include incisions from just a dozen of metres to 650 m, straight to highly meandering sections with sharp bends, well-developed levees and walls that reach 35° in slope gradient, hanging branches, conspicuous axial incisions and multiple knickpoints. Only the northernmost canyon indents in the continental shelf, whereas the others start at the limit between the upper and middle slopes, and are often fed by small, straight, leveed gullies. The action of both across-slope processes represented by submarine canyons and along-slope processes represented by terracing and scouring conform the ACM as a peculiar mixed margin, with the presence of both contour and gravity currents at the same place at the same time. We propose that at present, along-slope erosion and transport mainly occurs along the Perito Moreno terrace, whereas across-slope processes are much more dominant in the Nagera terrace. Erosive bedforms such as crescent scours, generated by contour currents, contribute to the progressive bottom-up erosion of the Nagera terrace and act as an initial collector of across-slope transported sediment, that later, due to flow focusing and recurrence, incise and interconnect creating definitive canyons that progress upslope by retrogressive erosion until their head indents the shelf break. Changes in the balance between across-slope and along-slope transport would imply a disequilibrium in the combination of processes leading to canyon formation, producing canyon abandonment, and partial or total filling. These changes could be produced by a variation in the depth of the main interfaces of Antarctic water masses leading to either an increase or a decrease in the erosion and transport capacity of contour currents, and/or by an enhancement of across-slope transport related to an increase of sediment availability.

Lastras, G.; Acosta, J.; Muñoz, A.; Canals, M.

2011-05-01

106

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

Federal Register 2010, 2011, 2012, 2013, 2014

...USCG-2013-0908] RIN 1625-AA00 Safety Zone, Submarine Cable Replacement Operations, Kent Island...their vessels on navigable waters during submarine cable replacement operations at the Kent...This rule involves the installation of a submarine cable within a federal navigation...

2013-11-08

107

Characterization of submarine canyon bathymetries in northern Ionian Sea, Italy, using sediment geochemical variation induced by transportation distance and basin depth  

NASA Astrophysics Data System (ADS)

Geochemical data of marine mud sediments collected from the Esaro, Neto and Corigliano canyons in the northern Ionian Sea (southern Italy) were investigated in order to characterize canyon bathymetry types. Mud sample compositions analyzed by the principal component analysis (PCA) provided useful information for the morphology of the depositional area of the northern Ionian Sea. The use of sediment geochemical data as well as transportation distance and depth as input variables for PCA enabled the extraction of following latent variables: basin depth (PC1), sedimentation rate (PC2) and transportation distance (PC3). Based on these results, we further developed geochemical indices that can estimate basin depth (F1), sedimentation rate (F2) and transportation distance (F3); these functions can be solely calculated from the elemental concentration data of the mud samples. Since these F1, F2 and F3 functions are mathematically independent variables, they facilitate more precise characterization of individual canyon types. That is, the Esaro Canyon is regarded as a sediment-starved deep canyon characterized by a single source area; the Neto Canyon can be seen as a deeply sloped submarine apron system and sediments are mainly supplied by the sediment gravity flows; the Corigliano Canyon is characterized by multiple sources and moderately sloped system, whose sediments disperse mainly by traction currents. These interpretations are concordant with the basin bathymetry of the studied area. Therefore, F1, F2 and F3 functions might be applicable to any oceanic basins.

Francesco, Perri; Tohru, Ohta; Salvatore, Critelli

2015-02-01

108

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

NASA Astrophysics Data System (ADS)

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

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

2010-05-01

109

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

PubMed Central

Cold-water corals are azooxanthellate species found throughout the ocean at water depths down to 5000 m. They occur in patches, reefs or large mound structures up to 380 m high, and as ecosystem engineers create important habitats for a diverse fauna. However, the majority of these habitats are now within reach of deep-sea bottom trawling. Many have been severely damaged or are under threat, despite recent protection initiatives. Here we present a cold-water coral habitat type that so far has been overlooked – quite literally – and that has received minimal impact from human activities. Vertical and overhanging cliffs in deep-sea canyons, revealed using an innovative approach to marine habitat mapping, are shown to provide the perfect substratum for extensive cold-water coral-based communities. Typical canyon-related processes, including locally enhanced internal tides and focussed downslope organic carbon transport, provide favourable environmental conditions (current regime, food input) to sustain the communities, even outside the optimal depth and density envelopes reported elsewhere in the NE Atlantic. Our findings show that deep-sea canyons can form natural refuges for faunal communities sensitive to anthropogenic disturbance, and have the potential to fulfil the crucial role of larval sources for the recolonisation of damaged sites elsewhere on the margin. PMID:22194903

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

2011-01-01

110

Defining biological assemblages (biotopes) of conservation interest in the submarine canyons of the South West Approaches (offshore United Kingdom) for use in marine habitat mapping  

NASA Astrophysics Data System (ADS)

In 2007, the upper part of a submarine canyon system located in water depths between 138 and 1165 m in the South West (SW) Approaches (North East Atlantic Ocean) was surveyed over a 2 week period. High-resolution multibeam echosounder data covering 1106 km2, and 44 ground-truthing video and image transects were acquired to characterise the biological assemblages of the canyons. The SW Approaches is an area of complex terrain, and intensive ground-truthing revealed the canyons to be dominated by soft sediment assemblages. A combination of multivariate analysis of seabed photographs (184-1059 m) and visual assessment of video ground-truthing identified 12 megabenthic assemblages (biotopes) at an appropriate scale to act as mapping units. Of these biotopes, 5 adhered to current definitions of habitats of conservation concern, 4 of which were classed as Vulnerable Marine Ecosystems. Some of the biotopes correspond to descriptions of communities from other megahabitat features (for example the continental shelf and seamounts), although it appears that the canyons host modified versions, possibly due to the inferred high rates of sedimentation in the canyons. Other biotopes described appear to be unique to canyon features, particularly the sea pen biotope consisting of Kophobelemnon stelliferum and cerianthids.

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

2014-06-01

111

Impact of Bottom Trawling on Deep-Sea Sediment Properties along the Flanks of a Submarine Canyon  

PubMed Central

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

112

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

NASA Astrophysics Data System (ADS)

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

Swarzenski, P. W.; Xu, J.

2008-12-01

113

Megalodicopia hians in the Monterey submarine canyon: Distribution, larval development, and culture  

NASA Astrophysics Data System (ADS)

The exclusively deep-sea ascidian family Octacnemidae comprises several genera in which the oral siphon has hypertrophied to form two large lips which create an "oral hood" capable of capturing motile prey. Megalodicopia hians is typical of this carnivorous family and has been reported to prey upon small epibenthic crustaceans. Distribution of M. hians in the Monterey Canyon system (36°45'N, 122°00'W) (California) was determined with remotely operated vehicles. M. hians was found sparsely to depths of at least 3800 m throughout the canyon; however, abundance was greatest within the oxygen-minimum zone (400-800 m). Eggs, sperm, and recently fertilized embryos were obtained repeatedly from adults returned to the laboratory in vivo, indicating that this species free-spawns routinely. Overall egg diameter (ovum plus chorion, plus follicle cells) was 175-190 ?m—considerably smaller than previously reported for this species. Embryonic development at temperature and oxygen concentrations equivalent to the oxygen-minimum zone was 2-4 d and, embryos gave rise to typical phlebobranch "simple" tadpole larvae. Larval period was extremely variable, and settlement/metamorphosis occurred up to 3 months post-hatching. These results are discussed within the context of settlement-site selection and fertilization ecology of the species.

Havenhand, Jon. N.; Matsumoto, George I.; Seidel, Ed

2006-02-01

114

Swept away by a turbidity current in Mendocino submarine canyon, California  

NASA Astrophysics Data System (ADS)

We present unique observations and measurements of a dilute turbidity current made with a remotely operated vehicle in 400 m water depth near the head of Mendocino Canyon, California. The flow had a two-layer structure with a thin (0.5 to 30 m), relatively dense (<0.04 vol %) and fast (up to ~1.7 m/s) wedge-shaped lower layer overlain by a thicker (up to 89 m) more dilute and slower current. The fast moving lower layer lagged the slow moving, dilute flow front by 14 min, which we infer resulted from the interaction of two initial pulses. The two layers were strongly coupled, and the sharp interface between the layers was characterized by a wave-like instability. This is the first field-scale data from a turbidity current to show (i) the complex dynamics of the head of a turbidity current and (ii) the presence of multiple layers within the same event.

Sumner, E. J.; Paull, C. K.

2014-11-01

115

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

116

Demography and movement patterns of leopard sharks (Triakis semifasciata) aggregating near the head of a submarine canyon along the open coast of southern California, USA  

USGS Publications Warehouse

The demography, spatial distribution, and movement patterns of leopard sharks (Triakis semifasciata) aggregating near the head of a submarine canyon in La Jolla, California, USA, were investigated to resolve the causal explanations for this and similar shark aggregations. All sharks sampled from the aggregation site (n=140) were sexually mature and 97.1 % were female. Aerial photographs taken during tethered balloon surveys revealed high densities of milling sharks of up to 5470 sharks ha-1. Eight sharks were each tagged with a continuous acoustic transmitter and manually tracked without interruption for up to 48 h. Sharks exhibited strong site-fidelity and were generally confined to a divergence (shadow) zone of low wave energy, which results from wave refraction over the steep bathymetric contours of the submarine canyon. Within this divergence zone, the movements of sharks were strongly localized over the seismically active Rose Canyon Fault. Tracked sharks spent most of their time in shallow water (?2 m for 71.0 % and ?10 m for 95.9 % of time), with some dispersing to deeper (max: 53.9 m) and cooler (min: 12.7 °C) water after sunset, subsequently returning by sunrise. These findings suggest multiple functions of this aggregation and that the mechanism controlling its formation, maintenance, and dissolution is complex and rooted in the sharks' variable response to numerous confounding environmental factors.

Nosal, D.C.; Cartamil, D.C.; Long, J.W.; Luhrmann, M.; Wegner, N.C.; Graham, J.B.

2013-01-01

117

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

SciTech Connect

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

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

1988-03-01

118

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

119

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

NASA Astrophysics Data System (ADS)

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

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

2009-05-01

120

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

121

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

122

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

123

Mapping the Canyon  

NSDL National Science Digital Library

In this activity, students will learn about the bathymetry of Hudson Canyon, a submarine canyon on the Atlantic coast of North America. As they study Hudson Canyon, they will compare and contrast topographic maps and bathymetric maps, investigate the various ways in which bathymetric maps are made, and learn how to interpret bathymetric maps.

124

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

PubMed Central

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

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

2012-01-01

125

Biophysical factors affecting the distribution of demersal fish around the head of a Submarine Canyon off the Bonney Coast, South Australia.  

PubMed

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

126

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

127

Architecture and development of a multi-stage Baiyun submarine slide complex in the Pearl River Canyon, northern South China Sea  

NASA Astrophysics Data System (ADS)

The Baiyun submarine slide complex (BSSC) along the Pearl River Canyon of the northern South China Sea has been imaged by multibeam bathymetry and 2D/3D seismic data. By means of maximum likelihood classification with slope aspect and gradient as inputs, the BSSC is subdivided into four domains, denoted as slide area I, II, III and IV. Slide area I is surrounded by cliffs on three sides and has been intensely reshaped by turbidity currents generated by other kinds of mass movement outside the area; slide area II incorporates a shield volcano with a diameter of approximately 10 km and unconfined slides possibly resulting from the toe collapse of inter-canyon ridges; slide area III is dominated by repeated slides that mainly originated from cliffs constituting the eastern boundary of the BSSC; slide area IV is distinguished by a conical seamount with a diameter of 6.5 km and a height of 375 m, and two slides probably having a common source that are separated from each other by a suite of residual strata. The BSSC is interpreted to be composed of numerous slide events, which occurred in the period from 10.5 to 5.5 Ma BP. Six specific factors may have contributed to the development of the BSSC, i.e., gas hydrate dissociation, gas-bearing sediments, submarine volcanic activity, seismicity, sedimentation rate and seafloor geomorphology. A 2D conceptual geological model combining these factors is proposed as a plausible mechanism explaining the formation of the BSSC. However, the BSSC may also have been affected by the Dongsha event (10 Ma BP) as an overriding factor.

Wang, Lei; Wu, Shi-Guo; Li, Qing-Ping; Wang, Da-Wei; Fu, Shao-Ying

2014-08-01

128

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

129

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

130

The Dnepr Canyon: evidence for a continuous submarine channel link between the outer shelf and the deep-sea basin of the northwestern Black Sea  

NASA Astrophysics Data System (ADS)

Multibeam bathymetric surveys and single-beam profiles were collected in 2003-2010 from aboard the Ukrainian RV Professor Vodyanitskiy (cruises PV-58 and PV-60, 2003 and 2004), and the German RV Meteor (cruise M-72, legs 1 and 4, 2007) and RV Maria S. Merian (cruise MSM-15, leg 2, 2010) along the continental margin of the NW Black Sea. Integrating published, reprocessed and novel data has revealed the existence of a major continuous channel extending from the Dnepr paleo-delta into greater water depths. It is more than 90 km long, 1.1 km wide and up to 125 m deep. On the upper slope (120-960 m water depth), a number of smaller channels merge into the large, Y-shaped Dnepr Canyon, which then continues obliquely downslope via this submarine channel to at least 1,815 m water depth off the Crimean continental margin, NW Black Sea. The channel could be an important, hitherto unknown link between the shallow oxic and deep anoxic environments of the Black Sea, along which sediment and organic matter could be funneled into the deep-sea basin. This would have far-reaching implications for investigations dealing with marine geology and biology, climate change, as well as oil and natural gas exploitation. The unusual alignment of the channel along the margin of the basin, as well as the location and mode of channel termination in deeper waters deserve future research.

Gulin, Sergei B.; Artemov, Yuriy G.; Egorov, Viktor N.; Evtushenko, Dmitriy B.

2013-08-01

131

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

SciTech Connect

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

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

1988-08-01

132

The Effect of Fang-Liao Earthquake on Particulate Scavenging and Transport Processes in the Gaoping Submarine Canyon Deduced from Pb-210 Observations  

NASA Astrophysics Data System (ADS)

Pb-210 were measured on the suspended particulate matter(SPM) and filtered water samples collected from five stations in the Gaoping Submarine Canyon (GPSC) during the 1201 cruise aboard R/V Ocean Researcher III in early January 2007, about two weeks after the Fang-Liao submarine earthquake (M > 6.5) occurred off southwest Taiwan. These stations were selected along the axis of the GPSC, and denoted as CW1 through CW5 sequentially from the shallow part near the mouth of the Gaoping River to the deep-water region of the canyon. The profile results of 210Pb determined from the 1201 cruise are compared with those at the same stations during the 1192 cruise aboard R/V Ocean Researcher III in late November 2006 to decipher the effect of earthquake on the particulate scavenging and lateral transport processes in this study area. The SPM concentrations measured from the 1201 cruise generally display an increase with depth, the values in the bottom water are more one order of magnitude higher than those observed above. The SPM profiles show a decrease away from the shore, the concentrations at CW1, CW2 and CW3 stations are an order of magnitude higher than those at CW4 and CW5 stations. The SPM spatial distribution trend of 1201 cruise is similar with that of 1192 cruise, but the SPM in the bottom water at all stations during 1201 cruise is from several to a few tens times higher than that from 1192 cruise, suggesting the effect of resuspension and slumping processes triggered by this submarine earthquake. The Pb-210 results observed during the 1201 cruise are described as below. The dissolved Pb-210 profiles generally show a decrease with depth, but an inverse trend is found in particulate Pb-210, responding to significant particulate scavenging. The mean values of particulate and dissolved Pb-210 obtained at CW1, CW2 and CW3 stations are respectively around 41-122 and 13-18 dpm/100kg and at other stations about 28-37 and 23-25 dpm/100kg, suggesting an increase toward offshore in dissolved Pb-210 and an inverse trend in particulate Pb-210 which are the same as trends observed from 1192 cruise. On the comparison of averages of particulate and dissolved Pb-210 activities between 1192 and 1201 cruises, the values (dpm/100kg) of particulate phase at all stations determined from 1201 cruise are two times higher than those from 1192 cruise, but the dissolved phase results from two cruise indicate no significant difference. According to the calculation of the particulate Pb-210 removal flux ratios from water column between 1201 and 1192 cruises, the values at CW2 and CW4 stations are around 1.0, and at other stations between 0.74 and 0.84, responding to the SPM dilution and particulate lateral transport processes.

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

2012-12-01

133

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

NASA Astrophysics Data System (ADS)

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

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

2010-12-01

134

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

135

Unusual occurrence and stratigraphic significance of the Glossifungites ichnofacies in a submarine paleo-canyon — Example from a Pliocene shelf-edge delta, Southeast Trinidad  

NASA Astrophysics Data System (ADS)

Sedimentary rocks belonging to the upper-slope shelf-margin delta of the Paleo-Orinoco River are present at the southeast coastline of Trinidad in the Columbus Basin. The Pliocene Mayaro Formation, exposed as foreshore cliffs, represents the wave-influenced delta front and mouth bar of this system. These deposits consist of thick to very thick hummocky cross-stratified sandstone beds and thin-bedded to laminated heterolithic sediments. They also contain abundant soft-sediment deformation structures and sparse well-preserved softground burrows (e.g. Ophiomorpha nodosa). Towards the north-central part of the outcrop, the delta front deposits are cut across by a paleo-canyon filled with younger mud-dominated prodeltaic sediments. The rare exposure of the canyon-wall exhibits an unusual occurrence of Glossifungites ichnofacies. Contrastingly distinct from archetypal examples, this monospecific suite contains a low abundance of firmground Thalassinoides filled with mud rather than sand. The tracemakers burrowed into a firm medium-grained sandy substrate of the delta front, and the burrows were subsequently passively filled by the mud from the overlying prodeltaic sediments filling the canyon. The deep-tier firmground Thalassinoides suite crosscuts the pre-existing softground trace fossils. Integration of ichnologic, sedimentologic and sequence-stratigraphic datasets indicates that the older delta front sediments are separated from the prodeltaic deposits by distinct episodes of fluctuating relative sea-level controlled by the basin-bounding growth-fault activities and the development of the canyon. Whereas the entire shelf-margin megasequence might have been deposited through a regional scale sea-level lowstand, the local fluctuations in accommodation space resulting from the growth-fault movements and the incision of the canyon were responsible for the shifting positions of the depositional architectural elements of the shelf-edge delta.

Dasgupta, Sudipta; Buatois, Luis A.

2012-08-01

136

Shallow-water longshore drift-fed submarine fan deposition (Moisie River Delta, Eastern Canada)  

E-print Network

ORIGINAL Shallow-water longshore drift-fed submarine fan deposition (Moisie River Delta, Eastern Submarine canyons and associated submarine fans are in some cases located at the end of a littoral cell to the discovery of an unusu- ally shallow submarine fan (60 m) located at the end of a littoral cell. Sediment

St-Ong, Guillaume

137

Sediment transport in the Mississippi Canyon: the role of currents and storm events on optical variability  

E-print Network

or submarine canyons, can act as conduits for particle flux (Nittrouer and Wright, 1994). Overlapping the region between deep-sea circulation and shelf dynamics, submarine canyons can be regions of complex fluid flow and enhanced mixing, and therefore... regions of enhanced transfer of chemical, biological, and physical properties between continental shelves and the continental slope and rise (Hotchkiss and Wunsch, 1982). Submarine canyons are a ubiquitous feature of continental slopes, but vary...

Burden, Cheryl A

1999-01-01

138

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

ERIC Educational Resources Information Center

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

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

139

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

140

Crustal deformation and submarine canyon incision in a Meso-Cenozoic first-order transfer zone (SW Iberia, North Atlantic Ocean)  

NASA Astrophysics Data System (ADS)

Using a dense grid of high-quality 2D seismic profiles, dredge and outcrop data, the offshore prolongation of a first-order transfer zone, the Messejana-Plasencia Fault Zone (MPFZ), is explained within the context of oblique rifting between Southwest Iberia, Newfoundland, and West Tethys. The offshore MPFZ is shown to comprise a 5-10 km wide region of deformation, oblique to the continental margin, reactivated in the Mesozoic as part of a wider transcurrent domain, the São Vicente sub-basin. Here, the geometry of faults and strata denotes the generation of a pull-apart basin during the Jurassic-Early Cretaceous. In contrast, its Late Cretaceous to Cenozoic evolution favours left-lateral transpression during the counter-clockwise rotation and eastward migration of Iberia towards its present position. Erosion was subsequently enhanced in the São Vicente sub-basin due to the reactivation of syn-rift structures. By documenting the evolution of the São Vicente sub-basin, and adjacent MPFZ, this work demonstrates: 1) the temporal and spatial scales in which first-order transfer zones accommodate crustal movements during continental rifting and subsequent inversion episodes; 2) the generation of an extensive region of strain accommodation in the vicinity of the MPFZ, an observation with profound implications to future palaeogeographic reconstructions of the North Atlantic Ocean; and 3) that the São Vicente Canyon, the physiographic expression of the MPFZ, incised the margin as early as the latest Cretaceous-Paleocene, synchronously with the onset of tectonic uplift in Southwest Iberia. In such a setting, the São Vicente sub-basin and MPFZ formed important by-pass corridors for sediment sourced from proximal areas of the margin. At present, the MPFZ comprises a complex releasing-restraining bend accommodating important vertical and horizontal movements in Southwest Iberia. Based on earthquake data from similar transfer zones, the MPFZ should be able to generate large-magnitude earthquakes and potentially destructive tsunamis.

Pereira, Ricardo; Alves, Tiago M.

2013-08-01

141

Morphology of late Quaternary submarine landslides along the U.S. Atlantic continental margin  

E-print Network

Morphology of late Quaternary submarine landslides along the U.S. Atlantic continental margin David bathymetry and backscatter imagery provides an opportunity to reevaluate the distribution of submarine categories based on their source areas: those sourced in submarine canyons and those sourced on the open

ten Brink, Uri S.

142

Interacting ocean waves explain powerful seafloor canyon flows  

NASA Astrophysics Data System (ADS)

Off the southwestern coast of Taiwan the Gaoping Submarine Canyon meanders in a giant backward S shape as it stretches southwestward toward the South China Sea. In the canyon, a 200-meter-deep cut into the seafloor that lies 300 meters below the sea's surface, the waters carry an usually large amount of internal tidal power—9.1 megawatts from the canyon's mouth to its head. Along with the strong flows a region of enhanced vertical mixing sits at the canyon's head. Researchers had previously attributed the anomalous flows to internal waves pushing through the Gaoping Canyon, though the source of the energy remained an open question.

Schultz, Colin

2012-02-01

143

Development of the Astoria Canyon-Fan physiography and comparison with similar systems  

USGS Publications Warehouse

A detailed bathymetric study of Astoria Canyon and Astoria Fan provides a model for typical submarine canyon-fan systems. The present canyon head is 9 miles (17 km) west of the Columbia River mouth but buried Pleistocene channels appear to have connected the two features in the past. The canyon, which is distinguished by its relief, V-shaped profiles, and numerous tributaries, winds sinuously and is coincident with apparent structural trends across the continental shelf and slope. At the fan apex, the canyon mouth merges smoothly into Astoria Channel, which is characterized by its U-shaped profiles, lower walls of even height, and levee development. Astoria Channel and the fan valley at the base of the continental slope are the most recently active of a series of main fan valleys that appear to have: (1) progressively "hooked left"; (2) migrated from north to south across the fan during its formation; and (3) been partly responsible for the asymmetrical shape of the fan. The deep, narrow upper fan valleys that characterize the steep (> 1:100, or 0??35???) and rough (10-30 fathoms, or 18-55 m) upper fan surface break into distributaries on the middle fan, where there is the sharpest change in gradient. The main valleys become broader and shallower down the fan, while the generally concave fan surface grades to nearly a flat seafloor (to gradients < 1:1000, or 0??0.5???), (< 10 fathoms, or 18 m relief). Similarity of Astoria Canyon-Fan system with other deep-sea fan and alluvial fan systems, suggests the hypothesis that size of drainage basin, sediment size, and sediment load control the size, gradient, and valley development of any fan system. Data from bathymetry, seismic refraction stations, and sediment load of the Columbia River indicate that the cutting of Astoria Canyon and the deposition of the unconsolidated sediment layer forming Astoria Fan could have been accomplished during the Pleistocene. A similar history can be suggested for other major submarine canyon-fan systems. ?? 1970.

Nelson, C.H.; Carlson, P.R.; Byrne, J.V.; Alpha, T.R.

1970-01-01

144

Marine geology of the Quaternary Bass Canyon system, southeast Australia: A cool-water carbonate system  

Microsoft Academic Search

The modern Bass Canyon is one of the world's largest submarine canyon systems that is entirely located within a cool-water carbonate environment. Five large shelf-breaching and three slope-confined tributary canyons coalesce on the lower slope and enter the massive deep-water Bass Canyon at 3000 m depth. Normal slope sediments consist predominantly of sandy calcilutite and muddy calcarenite interpreted as mud flow

J. K. Mitchell; G. R. Holdgate; M. W. Wallace; S. J. Gallagher

2007-01-01

145

Exploration models for submarine slope sandstones  

SciTech Connect

Recent published studies have demonstrated a far greater potential than previously recognized for submarine slope sandstones to contain significant oil and gas reserves in the Gulf Coast and elsewhere. Comparison of modern slopes with outcrop and subsurface analogs from several areas provided the framework for developing the following submarine slope sandstone exploration models: submarine canyon fill, slope gully/channel fill, slope spillover sand sheets, and intraslope basin fill. Submarine canyon fill is mainly shale, but sandstone beds that form stratigraphic traps may be present. Canyon shale fill juxtaposed against older sandstones can also form stratigraphic traps. Gully/channel fills are sandstones deposited on shallow-gradient slopes or ramps. The proximity of these sandstones to slope shales provides opportunities for stratigraphic traps to develop. Spillover sand sheets are resedimented from a shelf to a shallow-gradient slope and are associated with gully/channel fills. Intraslope basin fill is mainly shale, but elongate, sheetlike, or fan-shaped turbidite sandstones can provide stratigraphic traps. In all of these deposits, slope shales may be sufficiently enriched in organic carbon to be potential hydrocarbon source rocks; the potential for organic-rich shales to accumulate is highest in intraslope basin fill.

Slatt, R.M.

1986-09-01

146

The Nearshore Canyon Experiment  

NASA Astrophysics Data System (ADS)

Observations collected in Fall 2003 during the Nearshore Canyon Experiment (NCEX) will be used to test hypotheses about the effect of complex continental-shelf bathymetry on surface gravity waves and on wave-driven circulation. Refraction, diffraction, reflection, scattering, and trapping by abrupt shelf bathymetry can result in dramatic alongshore variations in wave height and direction. Onshore of the irregular bathymetry, alongcoast changes in breaking waves can force complicated circulation, including alongshore flows that reverse direction across the surf zone and along the shoreline, and strong offshore-directed rip currents that may be an important mechanism for transport of water, sediment, and pollution between the surf zone and inner shelf. Observations for NCEX will be obtained along the southern California coast near two steep submarine canyons (separated alongshore by a few km) that cross the shelf from about 300-m water depth to just seaward of the surfzone near Black's Beach (famous for large waves) and La Jolla Shores (well known as a calm area with small waves). Frequency-directional spectra of incident waves estimated from observations offshore of the canyons will be used to initialize models that predict the effect of the canyons on infragravity waves, swell, sea, and wave-driven circulation. Model predictions will be tested with observations from alongshore arrays deployed near, between, and onshore (including the surf and swash zones) of the canyons. Arrays also will be deployed to investigate wave reflection and scattering from the steep canyon walls, and cross-shore changes in surf and swash zone circulation. Additional instrumentation will be used to study alongcoast changes in wave breaking and set-up, details of surface currents in the surf and swash, and breaking-induced turbulence and dissipation. The NCEX instrument arrays will be designed in collaboration with modelers, and near-real time data will be used to initialize and test model predictions. In addition, model forecasts will be used to guide placement of movable sensors, allowing predictions of nearshore waves and currents to be tested during the observational period. NCEX~team~members~are~listed~on http://science.whoi.edu/PVLAB/NCEX/ncex.html. Funding for NCEX is provided by the US Office of Naval Research and the National Science Foundation.

Elgar, S.

2002-12-01

147

Genotype, soil type, and locale effects on reciprocal transplant vigor, endophyte growth, and microbial functional diversity of a narrow sagebrush hybrid zone in Salt Creek Canyon, Utah  

USGS Publications Warehouse

When addressing the nature of ecological adaptation and environmental factors limiting population ranges and contributing to speciation, it is important to consider not only the plant's genotype and its response to the environment, but also any close interactions that it has with other organisms, specifically, symbiotic microorganisms. To investigate this, soils and seedlings were reciprocally transplanted into common gardens of the big sagebrush hybrid zone in Salt Creek Canyon, Utah, to determine location and edaphic effects on the fitness of parental and hybrid plants. Endophytic symbionts and functional microbial diversity of indigenous and transplanted soils and sagebrush plants were also examined. Strong selection occurred against the parental genotypes in the middle hybrid zone garden in middle hybrid zone soil; F1 hybrids had the highest fitness under these conditions. Neither of the parental genotypes had superior fitness in their indigenous soils and habitats; rather F1 hybrids with the nonindigenous maternal parent were superiorly fit. Significant garden-by-soil type interactions indicate adaptation of both plant and soil microorganisms to their indigenous soils and habitats, most notably in the middle hybrid zone garden in middle hybrid zone soil. Contrasting performances of F1 hybrids suggest asymmetrical gene flow with mountain, rather than basin, big sagebrush acting as the maternal parent. We showed that the microbial community impacted the performance of parental and hybrid plants in different soils, likely limiting the ranges of the different genotypes.

Miglia, K.J.; McArthur, E.D.; Redman, R.S.; Rodriguez, R.J.; Zak, J.C.; Freeman, D.C.

2007-01-01

148

Genotype, soil type, and locale effects on reciprocal transplant vigor, endophyte growth, and microbial functional diversity of a narrow sagebrush hybrid zone in Salt Creek Canyon, Utah.  

PubMed

When addressing the nature of ecological adaptation and environmental factors limiting population ranges and contributing to speciation, it is important to consider not only the plant's genotype and its response to the environment, but also any close interactions that it has with other organisms, specifically, symbiotic microorganisms. To investigate this, soils and seedlings were reciprocally transplanted into common gardens of the big sagebrush hybrid zone in Salt Creek Canyon, Utah, to determine location and edaphic effects on the fitness of parental and hybrid plants. Endophytic symbionts and functional microbial diversity of indigenous and transplanted soils and sagebrush plants were also examined. Strong selection occurred against the parental genotypes in the middle hybrid zone garden in middle hybrid zone soil; F(1) hybrids had the highest fitness under these conditions. Neither of the parental genotypes had superior fitness in their indigenous soils and habitats; rather F(1) hybrids with the nonindigenous maternal parent were superiorly fit. Significant garden-by-soil type interactions indicate adaptation of both plant and soil microorganisms to their indigenous soils and habitats, most notably in the middle hybrid zone garden in middle hybrid zone soil. Contrasting performances of F(1) hybrids suggest asymmetrical gene flow with mountain, rather than basin, big sagebrush acting as the maternal parent. We showed that the microbial community impacted the performance of parental and hybrid plants in different soils, likely limiting the ranges of the different genotypes. PMID:21636412

Miglia, Kathleen J; McArthur, E Durant; Redman, Regina S; Rodriguez, Russell J; Zak, John C; Freeman, D Carl

2007-03-01

149

Upwelling flow dynamics in long canyons at low Rossby number  

NASA Astrophysics Data System (ADS)

Submarine canyons, topographic features incising the continental slope, vary in both shape and size. The dynamics of short canyons have been observed and described in the field, in the laboratory, and with numerical simulations. Flow within long canyons, such as Juan de Fuca canyon, located between Vancouver Island and Washington State in the Pacific Northwest, is less well understood. Physical models of both long and short canyons have been constructed to understand the upwelling dynamics in long canyons and how upwelling changes, as compared with the dynamics of short canyons, at low Rossby number. Stratification and rotation, both important parameters in determining the dynamics in canyons, can be controlled and scaled accordingly for replication of oceanic conditions. The physical model is spun up to an initial rotation rate, and the flow is forced by increasing the rotation rate over the equivalent of several days. Flow visualization is used to determine the strength and location of upwelling, the strength and mechanisms generating vorticity, as well as the differences between the flow within the long and short canyons. The pattern of upwelling between the two canyons is significantly different in the horizontal with upwelling occurring through the canyon head in the short canyon and upwelling occurring close to the mouth along the downstream rim in the long canyon. At high Rossby number, upwelling is similar in both the long and short canyon and is driven by advection. However, as Rossby number decreases, the flow in the long canyon is more strongly affected by the strong convergence of the isobaths near the canyon than by advection alone.

Waterhouse, Amy F.; Allen, Susan E.; Bowie, Alexander W.

2009-05-01

150

Simple Submarine  

NSDL National Science Digital Library

Using simple, inexpensive items, students build and test submarine models in a single class period. They gain insight into the engineering that's required to make these machines ascend, descend, and hover safely in extreme environments. The printable eight-page handout includes a series of inquiry-based questions that get students thinking about the complex engineering required for submersibles, illustrated experiment directions, and a worksheet that includes thought-provoking questions along with areas for recording experiment data.

151

Hot Canyon  

ScienceCinema

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

None

2013-03-01

152

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

153

Potential for SGD induced submarine geohazard off southwestern Taiwan  

NASA Astrophysics Data System (ADS)

The submarine groundwater discharge (SGD) is not only play important roles on material exchange between land and sea, it may also trigger liquefaction process and induce further submarine geohazards in coastal zone. Since 2006, Southern Taiwan was experienced a series of natural hazards including earthquakes and typhoon that induced severe landslides and flooding and caused huge human lives and economics losses. These natural hazards also touched off submarine cable-break incidents off southwestern Taiwan from Gaoping Slope to the northern terminus of the Manila Trench. After the 2006 Pingtung Earthquake, the local fishermen reported disturbed waters at the Fangliao submarine canyon head. Although many researches conjectured the disturbed waters may caused by the eruption of submarine volcanoes which has been widely discovered off the southwestern Taiwan. The subbottom profiles reveal a series of faults and liquefaction strata exist near the head of Fanliao submarine canyon and acoustically transparent sediments with doming structures also observed at the adjacent area. Moreover, we also found pockmarks with acoustic blanking under it on the Gaoping Shelf and a series of gaseous pluming gushed from the seafloor was also observed in the shallow waters. Integrate all these data, we may reasonably infer the disturbed waters which reported by the fishermen may caused by the liquefaction process on the seafloor. In addition to geophysical observations, natural geochemical tracers (radon and radium) in conjunction with side-scan sonar were used to evaluate the distribution of SGD system in the study area. All the evidences indicate that the large earthquake in conjunction with high pore fluid pressures in the surface sediment might have easily triggered liquefaction process and generated large debris flow and swept the submarine cables away from the Fangliao submarine canyon head to the abyss.

Su, C.; Lin, C.; Cheng, Y.; Chiu, H.

2013-12-01

154

Obstacle avoidance sonar for submarines  

NASA Astrophysics Data System (ADS)

The Advanced Mine Detection Sonar (AMDS) system was designed to operate in poor environments with high biological and/or shallow-water boundary conditions. It provides increased capability for active detection of volume, close-tethered, and bottom mines, as well as submarine and surface target active/passive detection for ASW and collision avoidance. It also provides bottom topography mapping capability for precise submarine navigation in uncharted littoral waters. It accomplishes this by using advanced processing techniques with extremely narrow beamwidths. The receive array consists of 36 modules arranged in a 15-ft-diameter semicircle at the bottom of the submarine sonar dome to form a chin-mounted array. Each module consists of 40 piezoelectric rubber elements. The modules provide the necessary signal conditioning to the element data prior to signal transmission (uplink) through the hull. The elements are amplified, filtered, converted to digital signals by an A/D converter, and multiplexed prior to uplink to the inboard receiver. Each module also has a downlink over which it receives synchronization and mode/gain control. Uplink and downlink transmission is done using fiberoptic telemetry. AMDS was installed on the USS Asheville. The high-frequency chin array for Virginia class submarines is based on the Asheville design.

Dugas, Albert C.; Webman, Kenneth M.

2002-05-01

155

Tectonic control of Cretaceous gravity deposits and submarine Valleys in the subalpine basin, French western Alps  

SciTech Connect

The Late Jurassic-Early Cretaceous series of the French subalpine basin is characterized by alternating limestones and marls with numerous, thick gravity-flow deposits (carbonate debris flows and slumps, siliciclastic grain flows, turbidites). These gravity deposits originate from platforms and slopes and come through the basin via several parallel canyons and submarine valleys. Some carbonate (Berriasian) and siliciclastic (Aptian) deep-sea fans are built at the canyon mouth during intense activity of the canyons and reworking of the sediments. The tectonic control of the gravity deposits is demonstrated by the position and filling of the submarine valleys all along the Cretaceous. The submarine valleys correspond systematically to the lower part of extensional tilted blocks; the gravity deposits come along the main syn-sedimentary normal faults delimiting these tilted blocks. The gravity deposits go from one tilted block to another through some synsedimentary passes which are induced by slight folding, perhaps related to an early diapirism at some nodes of extensional faults. The canyon-like valleys are due to very strong erosion when a submarine valley cuts of the higher part of a tilted block. The gravity deposits are stacked atop each other and progressively fill the valleys. Thus the cutting and filling of the submarine valleys and canyons on occasions during the Early Cretaceous are explained by a permanent synsedimentary activity. These Jurassic and Cretaceous extensional structures are later reactivated by inversion during Tertiary compressional movements.

Philippe, J.; Beaudoin, B.; Fries, G.; Parize, O.

1988-08-01

156

Design a Submarine  

NSDL National Science Digital Library

Learners act as engineers and design mini submarines that move in the water like real submarines. The submarines must be able to float, sink, and hover steadily without touching the top of the water or resting on the bottom. Use this activity to introduce learners to density and buoyancy.

2012-03-20

157

Seismic depth conversion problems associated with the Mississippi Canyon in the vicinity of Ewing Bank Block 305 field, offshore Louisiana  

Microsoft Academic Search

Ewing Bank Block 305 field is located on the outermost edge of the continental shelf, approximately 145 km south of New Orleans, Louisiana. The geology of the field is fairly typical of other fields found offshore of Louisiana, except there is a huge, partly filled, Pleistocene submarine canyon that overlies the field. This canyon, which is commonly referred to as

G. P. Leveille; K. S. Sahai; P. G. McDaniel

1990-01-01

158

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

159

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

160

Morphological features and forming mechanism of Central Canyon in the Qiongdongnan basin, northern South China Sea  

NASA Astrophysics Data System (ADS)

The Central Canyon in the Qiongdongnan basin, northern South China Sea, with an "S-shaped" geometry, trends NE across the Ledong-Lingshui, Songnan, Baodao and Changchang depressions. According to the morphology, filling and stratigraphic architectures, the Central Canyon can be divided into 4 types in shape: V, U, W, and Complex types, and 3 segments in aera: Eastern, Western and Transfer segments. The Transfer segment aparting the NE to NEE or EW striking of the canyon was coincided with the tectonic transfer zone, located in the Baodao depression. The formation and development of the Central Canyon was response of the tectonic activity and deep-water deposition. Eastern segment was controlled by submarine uplift, as barrier to limit the generation of Central Canyon in Huangliu Formation and supply the restricted channel for the later canyon. The West segemnt was associated with the deep-water deposition. The origin of the filling in the Central Canyon can be ascribed to the gravity sediment. At each stage, the generation of the Central Canyon is simultaneous to or a litter earlier than the one of contemporaneous slope, it can be proposed that the canyon formed initially at the east of Qiongdongnan basin and spread westwards gradually. The planar distribution of the Central Canyon The morphological classification of the Central Canyon

Su, M.; Xie, X.; Jiang, T.; Zhang, C.; Li, J.; Zhang, C.; He, Y.

2010-12-01

161

Deepwater canyons: An escape route for methane sealed by methane hydrate  

NASA Astrophysics Data System (ADS)

Three-dimensional seismic imaging and modelling of gas hydrates from offshore of west Africa (Mauritania) shows that submarine canyons on stable continental slopes can capture and release methane that is sealed by methane hydrate. We demonstrate this by focussing on a canyon which is ~ 200 km long, 2.4 to 3.1 km wide, up to 550 m deep and has canyon walls that dip at 25°-30°. Incision of the canyon causes cooling of the surrounding sediment and deepening of the base of the methane hydrate stability zone. The base of the hydrate deepens by up to 550 m and also dips at 25°-30°, parallel to the canyon margins. It forms a continuous or semi-continuous wall of lower permeability sediment that can be mapped along the canyon margins on the basis of aligned high amplitude reflection terminations. Theoretically these methane barriers could extend for 10 s to 100 s of kilometres parallel to both canyon walls. Several free gas accumulations are sealed laterally in this way in a canyon margin free gas zone. Large failures of the sides of the canyon, remove the lower permeability hydrate, allowing free methane to leak. Globally, submarine canyons and marine gas hydrates occur in similar places on continental margins and canyons incise to depths that are comparable with the position of base of the methane hydrate stability zone. Therefore deepening of the base of the hydrate as a result of the cooling effect of canyons should be common and this mechanism for methane trapping and release could be generally applicable to present and past marine methane hydrates.

Davies, Richard J.; Thatcher, Kate E.; Mathias, Simon A.; Yang, Jinxiu

2012-03-01

162

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

163

Morphology and forcing agents of the Monterey Canyon System: a quantitative geomorphic analysis  

NASA Astrophysics Data System (ADS)

Landforms are shaped by tectonics and climate, which control deformation, deposition, and erosion at the fluid/solid interface. The recent re-emergence of geomorphology was spurred by the realization that the shape of the land is not only the result of many processes, but it also affects them. Tectonics builds mountains and geomorphic agents and climate conditions modify them. Thus geomorphologic processes and tectonics are major agents of change and landform is the variable that links them, the expression of a steady-state equilibrium controlled by multiple feed-backs. Measuring and parameterizing the shape of the landscape is the first step in understanding many natural processes critical to environment, such as terrain instability and fluid circulation. Furthermore, a multidimensional parameterization of the land surface (e.g., geomorphic indices) is useful in comparing different landforms and in isolating the effect of specific factors, such as the level of tectonic activity. So far geomorphology has dealt primarily with land areas, but an expansion to the sub-aqueous environment is already in the making due to high-resolution bathymetry increase. This research compares submarine and land morphology as they manifest tectonics in a rapidly transform continental margin. To this end the research has analyzed high-resolution multibeam bathymetry to interpret modern submarine processes from a study of geomorphic change. This research is applied on the Monterey Bay (California) due to the complex geomorphology of both the Coast Ranges and the seafloor. Tectonic has controlled the evolution and the present geometry of the branches and meanders of the Monterey Canyon system, one of the largest submarine canyon systems in the world. In particular the Monterey Canyon is an erosional, presently active feature, which has resulted from both canyon cutting and mass wasting. The deeper parts of the canyon have been progressively offset from the headward part by strike-slip faulting, and are now located in northern Monterey Bay. In this context a clear understanding of the physical processes that trigger submarine slumps has been the basis of the research. The high-resolution multibeam record of the seafloor of the MBR collected by MBARI will be analyzed to measure the parameters describing the geometry of the submarine canyons of the Monterey Canyon System. Our quantitative geomorphologic analysis will include slope angle, sinuosity, and width of the canyon axis and of the thalweg. The interpretation of these geomorphologic parameters will help to define active processes along the submarine canyons of the MBR and to unveil the relationships between continental deformation and canyon formation in a transform continental margin. Moreover, to broaden constraints on geophysical properties and evolution of the area, we had used landform surface high resolution DEM.

Taramelli, A.; Aiello, I. W.; Melelli, L.; Seeber, L.; Sorichetta, A.

2007-12-01

164

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

165

Submarine cable route survey  

SciTech Connect

The growth of telecommunication market is very significant. From the beginning of the nineties, more and more the use of optical fiber submarine cables is privileged to that of satellites. These submarine telecommunication highways require accurate surveys in order to select the optimum route and determine the cable characteristics. Advanced technology tools used for these surveys are presented along with their implementation.

Herrouin, G.; Scuiller, T.

1995-12-31

166

Paint-Stirrer Submarine  

ERIC Educational Resources Information Center

In this article, the authors discuss a unique and challenging laboratory exercise called, the paint-stir-stick submarine, that keeps the students enthralled. The paint-stir-stick submarine fits beautifully with the National Science Education Standards Physical Science Content Standard B, and with the California state science standards for physical…

Young, Jocelyn; Hardy, Kevin

2007-01-01

167

THE SUBMARINE REVIEW SUMMER 2012  

E-print Network

THE SUBMARINE REVIEW 1 SUMMER 2012 SPURRING INNOVATION AT THE DECKPLATE LEVEL IN THE SUBMARINE FORCE LT Ryan P. Hilger, USN Submarine Student at the Naval Postgraduate School he phenomenal success to alter how we design and operate our submarines. Vice Admiral Richardson happily announced after

168

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

E-print Network

Reflection and tunneling of ocean waves observed at a submarine canyon Jim Thomson WHOI-MIT Joint Received 24 February 2005; accepted 7 April 2005; published 17 May 2005. [1] Ocean surface gravity waves: Thomson, J., S. Elgar, and T. H. C. Herbers (2005), Reflection and tunneling of ocean waves observed

Kirby, James T.

169

The Black Canyon of the Gunnison: Today and Yesterday  

USGS Publications Warehouse

Since the early visit of Captain John William Gunnison in the middle of the last century, the Black Canyon of the Gunnison has stirred mixed apprehension and wonder in the hearts of its viewers. It ranks high among the more awesome gorges of North America. Many great western canyons are as well remembered for their brightly colored walls as for their airy depths. Not so the Black Canyon. Though it is assuredly not black, the dark-gray tones of its walls and the hazy shadows of its gloomy depths join together to make its name well deserved. Its name conveys an impression, not a picture. After the first emotional impact of the canyon, the same questions come to the minds of most reflective viewers and in about the following order: How deep is the Black Canyon, how wide, how does it compare with other canyons, what are the rocks, how did it form, and how long did it take? Several western canyons exceed the Black Canyon in overall size. Some are longer; some are deeper; some are narrower; and a few have walls as steep. But no other canyon in North American combines the depth, narrowness, sheerness, and somber countenance of the Black Canyon. In many places the Black Canyon is as deep as it is wide. Between The Narrows and Chasm View in the Black Canyon of the Gunnison National Monument (fig. 15) it is much deeper than wide. Average depth in the monument is about 2,000 feet, ranging from a maximum of about 2,700 feet, north of Warner Point (which also is the greatest depth anywhere in the canyon), to a minimum of about 1,750 feet at The Narrows. The stretch of canyon between Pulpit Rock and Chasm View, including The Narrows, though the shallowest in the monument, is also the narrowest, has some of the steepest walls, and is, therefore, among the most impressive segments of the canyon (fig. 3). Profiles of several well-known western canyons are shown in figure 1. Deepest of these by far is Hells Canyon of the Snake, on the Idaho-Oregon border. Clearly, it dwarfs the Black Canyon in the immensity of its void, though its flaring walls lack the alarming verticality of the Black Canyon. Arizona's Grand Canyon of the Colorado is acknowledged as the greatest of them all; it is not as deep as Hells Canyon, but it is wider, longer, more rugged, and far more colorful. Its depth is two to three times that of the Black Canyon. Zion Canyon, Utah, combines depth, sheerness, serenity, and color in a chasm that ranges from capacious to extremely narrow. Its Narrows have a depth-to-width ratio unmatched by any other major American canyon. California's Yosemite Valley, in a setting of sylvan verdure, is unique among the gorges shown in profile in figure 1 in being the only glacial trough; its monolithic walls bear witness to the abrasive power of moving ice. Few cliffs in the world match the splendor of its El Capitan. Lodore Canyon, on the Green River in Dinosaur National Monument, Colorado, is best known, perhaps, for its noisy splashy rapids, first made famous by John Wesley Powell. Lodore Canyon also features towering cliffs of deep-red quartzite. Grand Canyon of the Yellowstone River, Wyoming, is noted for its great waterfalls, dashing river, and bright coloration. The Royal Gorge of the Arkansas River, Colorado, features the 'world's highest suspension bridge'. The profiles shown in figure 1 afford some basis for comparing one canyon with another. They cannot abstract in two dimensions the overall impression that each canyon makes. Color, vegetation, outcrop habit, vantage point, season of year, length of visit - even the roar of the river or lack thereof - all contribute to this highly personal effect. For a river of its size, the Gunnison has an unusually steep gradient through the Black Canyon. The river falls about 2,150 feet from the head of the canyon at Sapinero to the mouth at its junction with North Fork - a distance of about 50 miles and an average rate of fall of about 43 feet per mile. By comparison, the Green

Hansen, Wallace R.

1965-01-01

170

Grand Canyon University Portland State University Grand Canyon University  

E-print Network

Grand Canyon University Portland State University Grand Canyon University Transfer Worksheet College-level transferable academic courses taken at Grand Canyon University (GCU) will transfer. Academic Major Requirements 2. Degree Requirements (BA, BS) 3. General Education Requirements #12;Grand

Caughman, John

171

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

2010-08-20

172

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.

Huber, Patrick

2009-01-01

173

Seismic stratigraphy and salt tectonics of the Alaminos Canyon area, Gulf of Mexico.  

E-print Network

and by influencing the direction of mass transport. The uplift of the salt has formed topographic lows in which sediment is transported from the shelf beyond the slope. Within the study area, intraslope basins consist of remnants of submarine canyons blocked...

Mechler, Suzanne Marie

1994-01-01

174

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.

James Cameron

2013-01-01

175

Bryce Canyon Amphitheater Hoodoos  

USGS Multimedia Gallery

Bryce Canyon is a unique sandstone formation in southern Utah. It is home to a large number of hoodoos, which are oddly shaped pillars of rock that formed due to different erosion rates for the dolomite that caps them and the sandstone that forms their base. Bryce Canyon is also home to large numbe...

176

Bryce Canyon Hoodoos  

USGS Multimedia Gallery

Bryce Canyon is a unique sandstone formation in southern Utah. It is home to a large number of hoodoos, which are oddly shaped pillars of rock that formed due to different erosion rates for the dolomite that caps them and the sandstone that forms their base. Bryce Canyon is also home to large numbe...

177

Bryce Canyon Hoodoo  

USGS Multimedia Gallery

Bryce Canyon is a unique sandstone formation in southern Utah. It is home to a large number of hoodoos, which are oddly shaped pillars of rock that formed due to different erosion rates for the dolomite that caps them and the sandstone that forms their base. Bryce Canyon is also home to large numbe...

178

Bryce Canyon Hoodoo  

USGS Multimedia Gallery

Views along the Queen's Garden Trail in Bryce Canyon National Park. Bryce Canyon is a unique sandstone formation in southern Utah. It is home to a large number of hoodoos, which are oddly shaped pillars of rock that formed due to different erosion rates for the dolomite that caps them and the sands...

179

Bryce Canyon Cedars  

USGS Multimedia Gallery

Bryce Canyon is a unique sandstone formation in southern Utah. It is home to a large number of hoodoos, which are oddly shaped pillars of rock that formed due to different erosion rates for the dolomite that caps them and the sandstone that forms their base. Bryce Canyon is also home to large numbe...

180

Bryce Canyon Amphitheater  

USGS Multimedia Gallery

Bryce Canyon is a unique sandstone formation in southern Utah. It is home to a large number of hoodoos, which are oddly shaped pillars of rock that formed due to different erosion rates for the dolomite that caps them and the sandstone that forms their base. Bryce Canyon is also home to large numbe...

181

Bryce Canyon Hoodoos  

USGS Multimedia Gallery

Sandstone hoodoos in Bryce Canyon National Park. In the background, Grand Staircase-Escalante National Monument can be seen. Bryce Canyon is a unique sandstone formation in southern Utah. It is home to a large number of hoodoos, which are oddly shaped pillars of rock that formed due to different er...

182

Hoodoos of Bryce Canyon  

USGS Multimedia Gallery

Bryce Canyon is a unique sandstone formation in southern Utah. It is home to a large number of hoodoos, which are oddly shaped pillars of rock that formed due to different erosion rates for the dolomite that caps them and the sandstone that forms their base. Bryce Canyon is also home to large numbe...

183

Bryce Canyon Sandstone  

USGS Multimedia Gallery

Bryce Canyon is a unique sandstone formation in southern Utah. It is home to a large number of hoodoos, which are oddly shaped pillars of rock that formed due to different erosion rates for the dolomite that caps them and the sandstone that forms their base. Bryce Canyon is also home to large numbe...

184

Bryce Canyon Hoodoos  

USGS Multimedia Gallery

Views along the Queen's Garden Trail in Bryce Canyon National Park. Bryce Canyon is a unique sandstone formation in southern Utah. It is home to a large number of hoodoos, which are oddly shaped pillars of rock that formed due to different erosion rates for the dolomite that caps them and the sands...

185

Bryce Canyon Amphitheater  

USGS Multimedia Gallery

Views along the Queen's Garden Trail in Bryce Canyon National Park. Bryce Canyon is a unique sandstone formation in southern Utah. It is home to a large number of hoodoos, which are oddly shaped pillars of rock that formed due to different erosion rates for the dolomite that caps them and the sands...

186

Bryce Canyon's Cedar Valley  

USGS Multimedia Gallery

Bryce Canyon is a unique sandstone formation in southern Utah. It is home to a large number of hoodoos, which are oddly shaped pillars of rock that formed due to different erosion rates for the dolomite that caps them and the sandstone that forms their base. Bryce Canyon is also home to large numbe...

187

Bryce Canyon Amphitheater Panorama  

USGS Multimedia Gallery

Bryce Canyon is a unique sandstone formation in southern Utah. It is home to a large number of hoodoos, which are oddly shaped pillars of rock that formed due to different erosion rates for the dolomite that caps them and the sandstone that forms their base. Bryce Canyon is also home to large numbe...

188

Bryce Canyon Benchmark  

USGS Multimedia Gallery

A USGS elevation benchmark in Bryce Canyon National Park. Bryce Canyon is a unique sandstone formation in southern Utah. It is home to a large number of hoodoos, which are oddly shaped pillars of rock that formed due to different erosion rates for the dolomite that caps them and the sandstone that ...

189

Bryce Canyon Rim  

USGS Multimedia Gallery

The rim of Bryce Canyon, viewed from Rainbow Point. Bryce Canyon is a unique sandstone formation in southern Utah. It is home to a large number of hoodoos, which are oddly shaped pillars of rock that formed due to different erosion rates for the dolomite that caps them and the sandstone that forms ...

190

Bryce Canyon Natural Bridge  

USGS Multimedia Gallery

The Bryce Canyon Natural Bridge. Technically, this is not a natural bridge, which forms when running water erodes a tunnel into a rock formation. Instead, this is a natural arch, similar to the ones in nearby Arches National Park. Bryce Canyon is a unique sandstone formation in southern Utah. It is...

191

Hoodoos of Bryce Canyon  

USGS Multimedia Gallery

Views along the Queen's Garden Trail in Bryce Canyon National Park. Bryce Canyon is a unique sandstone formation in southern Utah. It is home to a large number of hoodoos, which are oddly shaped pillars of rock that formed due to different erosion rates for the dolomite that caps them and the sands...

192

Bryce Canyon Vistas  

USGS Multimedia Gallery

Views along the Queen's Garden Trail in Bryce Canyon National Park. Bryce Canyon is a unique sandstone formation in southern Utah. It is home to a large number of hoodoos, which are oddly shaped pillars of rock that formed due to different erosion rates for the dolomite that caps them and the sands...

193

Bryce Canyon Natural Bridge  

USGS Multimedia Gallery

Bryce Canyon's Natural Bridge is technically a natural arch, similar to those in the nearby Arches National Park. Bryce Canyon is a unique sandstone formation in southern Utah. It is home to a large number of hoodoos, which are oddly shaped pillars of rock that formed due to different erosion rates...

194

Glen Canyon Dam  

USGS Multimedia Gallery

The USGS Glen Canyon Adaptive Management Working Group took a trip in August from Glen Canyon Dam to Lees Ferry on Friday, August 31, 2012. This spot at Four Mile (four miles downstream from the dam) is where a lot of people fish: There were fishermen that day that claimed to have c...

195

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

196

Snake Hells Canyon Subbasin Inventory  

E-print Network

Snake Hells Canyon Subbasin Inventory May 2004 Prepared for the Northwest Power and Conservation .................................................................................................................................. 62 8 APPENDIX A APRE SUMMARIES FOR HELLS CANYON SUBBASIN.................. 63 Snake Hells Canyon Subbasin Inventory i May 2004 #12;LIST OF FIGURES FIGURE 1.LAND MANAGEMENT IN THE SNAKE HELLS CANYON

197

Tlie Submarine Caves of Bermuda  

E-print Network

Tlie Submarine Caves of Bermuda ThomasM. Iliffe Bermuda Biological Station, Ferry Reach 1-15 #12;The SubmarineCavesofBermuda ThomasM.Iliffe BermudaBiological Station,Ferry Reach 1-15 Abstract Bermuda the volcanic pedistal. Three types of submarine limestone cave morphology have so far been identified

Iliffe, Thomas M.

198

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

199

Submarine: Soda Cup Lander  

NSDL National Science Digital Library

In this activity (on page 2), learners create a submarine using a plastic cup. This is a fun way to learn about buoyancy and density. Extensions for this activity, such as adding a propeller or manometer, are also included.
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. Learners will also need an adult's help if they use a glue gun to attach the film canister to the plastic cup.

James Cameron

2013-01-01

200

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.

Jocelyn Young

2007-02-01

201

The Grand Canyon  

NSDL National Science Digital Library

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

Brieske, Joel A.

2002-01-01

202

Quantification of Upwelling through Steep Continental Shelf Canyons  

NASA Astrophysics Data System (ADS)

Submarine canyons that cut into the continental shelf are regions of enhanced upwelling during coast-wide upwelling events. Enhanced upwelling can occur due to four different processes: time dependence- the strength of shelf-flow is increasing allowing cross-isobath flow, advection- the small spatial scales of the canyon allow strong flow to cross-isobaths, isobath convergence- isobath convergence in the region of the canyon allows cross-isobath flow and a new process that appears to be related to internal waves which allows cross-isobath flow near the mouth of the canyon. We will briefly review these different types of upwelling, the flow patterns and dynamics associated with each. Then we will focus on the usually dominant advection-driven upwelling. The depth of upwelling and flux through the canyons quantifies this exchange between the shelf and the open ocean. Scaling analysis that relate these quantities to the strength of the flow, stratification, Coriolis parameter and topographic shape parameters allow their estimation in the absence of a full numerical simulation or a detailed field study of a specific canyon. Here we add the impact of the continental shelf slope to the scaling and test the scaling using a three-dimensional primitive equation model over 18 distinct geometries. The impact of the continental shelf is significant for real canyons with changes in the depth of upwelling of 20% and of the flux of upwelling of 65%. Including the continental slope, the depth of upwelling (as given by the three-dimensional model) can be estimated to within 10% and the upwelling flux (as given by the three-dimensional model) within 25%.

Allen, Susan; Howatt, Tara

2013-04-01

203

Coastal and submarine instabilities distribution in the tectonically active SW margin of the Corinth Rift (Psathopyrgos, Achaia, Greece)  

NASA Astrophysics Data System (ADS)

The Corinth Rift, one of the most active rifts in the world as local extension trending NE-SW reaches the amount of 14±2 mm/yr, corresponds to one of the largest zones of seismically active normal faulting. The formation, growth and migration southwards of the prevailing fault systems, which evolve simultaneously with the intense morphogenetic processes, are overprinted in the age, facies and thickness of the Plio-Pleistocene sequences constructing the south margin of the western Gulf of Corinth. The dominant fault blocks, defined by east-west trending, north dipping normal faults, are accompanied by several morphological features and anomalies, noticed in both the terrestrial and the marine environment. Our main aim has been to examine how the tectonic evolution, in combination with the attendant fierce erosional and sedimentary processes, has affected the morphology through geodynamic processes expressed as failures in the wider coastal area. High resolution multibeam bathymetry in combination with the available land surface data have contributed to submarine and subaerial morphological mapping. These have been used as a basis for the detection of all those geomorphic features that indicate instabilities probably triggered, directly or indirectly, by the ongoing active tectonic deformation. The interpretation of the combined datasets shows that the southwestern margin of the Corinth Rift towards Psathopyrgos fault zone is characterized by intense coastal relief and a narrow, almost absent, continental shelf, which passes abruptly to steep submarine slopes. These steep slope values denote the effects of the most recent brittle deformation and are related to coastal and submarine instabilities and failures. High uplift rates and rapid sedimentation, indicative of the regional high-energy terrestrial and submarine environment, are subsequently balanced by the transportation of the seafloor currents, especially where slope gradients decrease, disintegrating the probable slide deposits. Conversely, the nearby active -but older- tectonic structure of the Heliki fault, is related to less steep slopes. Canyons are extensive and sediment mass failures appear as retrogressive landslide scars identified near the headwalls. The mass movements evolving near the coastal and shallow marine areas may have a high tsunamigenic potential, which depends on the volumes of the mobilized materials. As a special interest has been arisen nowadays concerning risk assessment and management, the results of our study can be further evaluated from a geohazard perspective.

Simou, Eirini; Papanikolaou, Dimitrios; Lykousis, Vasilios; Nomikou, Paraskevi; Vassilakis, Emmanuel

2014-05-01

204

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

205

Superelevation and overspill control secondary flow dynamics in submarine channels  

NASA Astrophysics Data System (ADS)

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

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

2013-08-01

206

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

207

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.

208

Making a Submarine.  

ERIC Educational Resources Information Center

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

Cornacchia, Deborah J.

2002-01-01

209

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

210

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

211

Submarine Paleoseismology Based on Turbidite Records  

E-print Network

Submarine Paleoseismology Based on Turbidite Records Chris Goldfinger College of Oceanic trigger processes such as turbidity currents, submarine landslides, tsunami (which may be recorded both counterparts. This article reviews the use of submarine turbidite deposits for paleoseismology, focuses

Goldfinger, Chris

212

Arctic Submarine Slope Stability  

NASA Astrophysics Data System (ADS)

Submarine landsliding represents aside submarine earthquakes major natural hazard to coastal and sea-floor infrastructure as well as to coastal communities due to their ability to generate large-scale tsunamis with their socio-economic consequences. The investigation of submarine landslides, their conditions and trigger mechanisms, recurrence rates and potential impact remains an important task for the evaluation of risks in coastal management and offshore industrial activities. In the light of a changing globe with warming oceans and rising sea-level accompanied by increasing human population along coasts and enhanced near- and offshore activities, slope stability issues gain more importance than ever before. The Arctic exhibits the most rapid and drastic changes and is predicted to change even faster. Aside rising air temperatures, enhanced inflow of less cooled Atlantic water into the Arctic Ocean reduces sea-ice cover and warms the surroundings. Slope stability is challenged considering large areas of permafrost and hydrates. The Hinlopen/Yermak Megaslide (HYM) north of Svalbard is the first and so far only reported large-scale submarine landslide in the Arctic Ocean. The HYM exhibits the highest headwalls that have been found on siliciclastic margins. With more than 10.000 square kilometer areal extent and app. 2.400 cubic kilometer of involved sedimentary material, it is one of the largest exposed submarine slides worldwide. Geometry and age put this slide in a special position in discussing submarine slope stability on glaciated continental margins. The HYM occurred 30 ka ago, when the global sea-level dropped by app. 50 m within less than one millennium due to rapid onset of global glaciation. It probably caused a tsunami with circum-Arctic impact and wave heights exceeding 130 meters. The HYM affected the slope stability field in its neighbourhood by removal of support. Post-megaslide slope instability as expressed in creeping and smaller-scaled slides are the consequence. Its geometrical configuration and timing is different from submarine slides on other glaciated continental margins. Thus, it raises the question whether slope stability within the Arctic Ocean is governed by processes specific to this environment. The extraordinary thick slabs (up to 1600 m) that were moved translationally during sliding rise the question on the nature of the weak layers associated with this process. Especially theories involving higher pore pressure are being challenged by this observation, because either extreme pore pressures or alternative explanations (e.g. mineralogical and/or textural) can be considered. To assess the actual submarine slope stability and failure potential in the Arctic Ocean, we propose to drill and recover weak layer material of the HYM from the adjacent intact strata by deep drilling under the framework of Integrated Ocean Drilling Program. This is the only method to recover weak layer material from the HYM, because the strata are too thick. We further propose to drill into the adjacent deforming slope to identify material properties of the layers acting as detachment and monitor the deformation.

Winkelmann, D.; Geissler, W.

2010-12-01

213

Regional characteristics, timing, and significance of dissolution and collapse features in Lower Cretaceous carbonate platform strata, Desoto Canyon area, offshore Alabama-Florida  

E-print Network

begins to be subaqueously exposed here and makes up the present day Western Florida Escarpment. Submarine relief on the modern escarpment increases southward to 1500 meters (Figure 8). In the southern portion of the DeSoto Canyon protraction area..., the modem escarpment becomes progressively more erosional with submarine exposures of Lower Cretaceous inner platform facies and downfaulting of more basinward strata (Figure 8). Others authors have interpreted reefal buildups along the platform margin...

Iannello, Christine

2001-01-01

214

Experiments on hydraulic jumps in turbidity currents near a canyon-fan transition.  

PubMed

The point at which a submarine canyon debouches on its associated abyssal fan is generally characterized by a drop in channel slope. Turbidity currents of the kind responsible for the genesis of the canyon and fan should display an internal hydraulic jump near the slope transition. No direct field observations of any such jump appear, however, to have been made. Experiments on the nature of the jump and the resulting sedimentary deposits indicate that the thickness of the deposits just downstream of the jump tends to increase as the ratio of bed shear velocity immediately behind the jump to particle fall velocity decreases. PMID:17744147

Garcia, M; Parker, G

1989-07-28

215

Snake Hells Canyon Subbasin Assessment  

E-print Network

Snake Hells Canyon Subbasin Assessment May 2004 Prepared for the Northwest Power and Conservation, Ecovista Angela Sondenaa, Nez Perce Tribe Darin Saul, Ecovista #12;Snake Hells Canyon Subbasin Assessment Table of Contents 0 INTRODUCTION TO SNAKE HELLS CANYON SUBBASIN ASSESSMENT............ 1 1 SUBBASIN

216

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.

217

Submarine landslides: advances and challenges  

Microsoft Academic Search

Due to the recent development of well-integrat ed surveying techniques of the sea-floor, significant improvements were achieved in mapping and describing the morphology of submarine mass movements. Except for the occurrence of turbidity currents, the aquatic environment (marine and fresh water) experiences the same type of mass failure as found on land. Submarine mass movements however, can have run out

Jacques Locat; Homa J. Lee

2002-01-01

218

Mars: Canyon and Volcanoes  

NSDL National Science Digital Library

This image of Mars includes a brief description and a zoom-in feature to view the image at closer range. The center of the scene shows the entire Valles Marineris canyon system. An audio option allows one to listen to the caption. A glossary is also provided.

219

Camp Pendleton Kings Canyon  

E-print Network

Camp Pendleton Marine Corps Base Kings Canyon National Park China Lake Naval Weapons Center Edwards-Borrego Desert State Park Sequoia National Forest Los Padres National Forest Angeles National Forest San Bernardino National Forest Cleveland National Forest Sierra National Forest Joshua Tree National Park Death

220

Glen Canyon Dam  

USGS Multimedia Gallery

The Glen Canyon Dam on the Colorado River in Arizona. At noon Monday, Nov. 19, U.S. Interior Secretary Ken Salazar will open the dam’s river outlet tubes, releasing controlled flows larger than the usual 8,000-25,000 cubic feet per second that flows through the turbines of the Glen...

221

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.

222

Bryce Canyon National Park  

NSDL National Science Digital Library

The Bryce Canyon National Park website contains geology, history, and nature reference sections as well as maps, a photo gallery, and information for planning a trip to the park. The kids page includes the GeoDetectives earth history and physical earth science program. This program has units on earth systems, rocks and minerals, landforms, hydrology, plate tectonics, and paleontology.

223

Current submarine atmosphere control technology.  

PubMed

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

Mazurek, W

1998-01-01

224

Mapping the True 3D Morphology of Deep-Sea Canyons  

NASA Astrophysics Data System (ADS)

The importance of submarine canyons as ecosystem hotspots and sediment transport pathways has been recognised for decades (e.g. Heezen et al., 1955; Vetter & Dayton, 1998). However, studying canyon systems in detail is a challenge, because of the complexity and steepness of the terrain. Acoustic surveys are hampered by side-echoes, while the high slope angles cause most types of sampling equipment, deployed from surface vessels, to fail. Ship-borne bathymetric surveys tend to represent the canyon topography in an overly smoothed way as a result of their limited resolution in deep water compared to the scale of the terrain variability. Moreover, it is clear that overhanging cliffs cannot be mapped correctly with traditional, downward looking multibeam echosounders. The increasing availability of underwater vehicles, however, opens new opportunities. During summer 2009, we mapped several submarine canyon habitats in detail, using the UK deep-water Remotely Operated Vehicle (ROV) ISIS. In particular, we developed a new methodology to map vertical cliffs and overhangs by placing the high-resolution Simrad SM2000 multibeam system of the ROV in a forward-looking position rather than in the traditional downward-looking configuration. The cliff morphology was then mapped by moving the ROV laterally in parallel passes at different depths. Repeating this approach at different distances from the cliff face, we obtained maps of varying resolution and extent. The low resolution maps provide an overview of the general geological framework, while individual strata and faunal colonies can be recognised on the highest resolution maps. Using point-cloud models, we combined the ship-borne bathymetry with the ROV-based data, in order to obtain a true 3D seabed morphology of the canyon study site, which can be used for fly-throughs, geomorphological analysis or habitat mapping. With this approach, we could visualise the spatial structure and density distribution of a unique and previously unknown cold-water coral reef, formed as a hanging garden under a 1600 m long and 120 m high overhanging wall, at 1350 m water depth in the Whittard Canyon, NE Atlantic margin. Heezen, B.C., Ewing, M. and Menzies, R. (1955). The influence of submarine turbidity currents on abyssal productivity. Oikos, 6, 170-182. Vetter, E.W. & Dayton, P.K. (1998). Macrofaunal communities within and adjacent to a detritus-rich submarine canyon system. Deep-Sea Research II, 45, 25-54.

Huvenne, V. A.; Masson, D.; Tyler, P. A.; Huehnerbach, V.

2010-12-01

225

Seismic depth conversion problems associated with the Mississippi Canyon in the vicinity of Ewing Bank Block 305 field, offshore Louisiana  

SciTech Connect

Ewing Bank Block 305 field is located on the outermost edge of the continental shelf, approximately 145 km south of New Orleans, Louisiana. The geology of the field is fairly typical of other fields found offshore of Louisiana, except there is a huge, partly filled, Pleistocene submarine canyon that overlies the field. This canyon, which is commonly referred to as the Mississippi Canyon, causes a large seismic depth conversion problem that makes it virtually impossible to correctly map the structure of the field using normally processed marine seismic data The Mississippi Canyon is a large erosional feature that was formed at the mouth of the ancestral Mississippi River during the last glacial sea level lowstand. In the vicinity of the field, the canyon is about 10 km wide and 1 km deep, which is approximately two-thirds the size of the Grand Canyon of the Colorado River, and is filled mostly with Holocene sediments. Because the sediments that fill the canyon are very young, their interval velocities are much lower than the interval velocities of the sediments that form the canyon walls. This creates abrupt near surface lateral velocity variations that distort the geometry of seismic reflectors such that the time geometries seen on seismic lines are not at all indicative of the structure of the subsurface. Using a model-based processing technique and available well control, the authors have been able to solve this difficult depth conversion problem and have gained a better understanding of the geology of this field.

Leveille, G.P. (Conoco Inc., New Orleans, LA (USA)); Sahai, K.S.; McDaniel, P.G.

1990-05-01

226

Optimizing submarine berthing with a persistence incentive  

Microsoft Academic Search

Submarine berthing plans reserve mooring locations for inbound U.S. Navy nuclear submarines prior to their port entrance. Once in port, submarines may be shifted to different berthing locations to allow them to better receive services they require or to make way for other shifted vessels. However, submarine berth shifting is expensive, labor inten- sive, and potentially hazardous. This article presents

Gerald G. Brown; Kelly J. Cormican; Siriphong Lawphongpanich; Daniel B. Widdis

1997-01-01

227

Evidence for submarine landslides and continental slope erosion related to fault reactivation during the last glaciation offshore eastern Canada  

NASA Astrophysics Data System (ADS)

Many studies have proposed that reactivation of dormant faults during deglaciation is a source of neotectonic activity in glaciated regions, but few have demonstrated the relationship to submarine landslides. In this study, seabed morphology and shallow geology of the outer continental margin adjacent to the Charlie Gibbs Fracture Zone off Newfoundland, Canada was investigated for evidence of this relationship. The glacial history and morphology of the margin suggest that the entire continental shelf in the area, coincident with major continental crustal lineaments, was ice-covered during the Last glacial cycle, and transverse troughs delineate the paleo-icestream drainage patterns. A recent investigation of Notre Dame Trough revealed the existence of large sediment failures on the shelf. The current study investigates complex seafloor erosion and widespread mass transport deposition (MTD) on the continental slope seaward of Notre Dame Trough, using recently-acquired high resolution seismic reflection data and piston cores. The new data reveal that a trough mouth fan (TMF) is present on the slope seaward of Notre Dame Trough. The Notre Dame TMF is characterized by a succession of stacked debris flows, but does not show a lobate shape in plan view like other classic TMFs. Instead, the Notre Dame TMF has abruptly-truncated margins suggesting post-depositional failure and erosion of the fan deposits. Seismic reflection data show that the locations of the failures along the TMF margin are coincident with a set of shallow faults; however the current dataset does not image the deeper portion of the faults. On the upper slope immediately south of the TMF, a narrow and deeply incised canyon is located along-trend with the Notre Dame Trough. The location of this canyon appears to be controlled by a fault. Downslope from this canyon, along the southern margin of the TMF, a 25 km wide, flat-floored, U-shaped valley was eroded into a succession of stacked MTD-filled channels. Seismic stratigraphic analysis shows that the valley developed around the same time as the adjacent TMF, however, the valley morphology and evidence for repeated slope failure suggests that the processes responsible for its formation were different than the processes that formed the nearby TMF. Age control provided from piston cores suggest that the last major slope failure that contributed to valley formation probably occurred at ~29 ka. Geotechnical measurements from piston cores show slightly underconsolidated sediments. The results indicate that this part of the margin is more unstable than Orphan Basin and Labrador slope regions. Given the low factor of safety and the complex fault system, low energy earthquake from the surrounding area could be enough to potentially trigger landslides.

Saint-Ange, F.; Campbell, C.; MacKillop, K.; Mosher, D. C.; Piper, D. J.; Roger, J.

2012-12-01

228

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

229

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

230

The Grand Canyon  

NSDL National Science Digital Library

This lesson plan is part of the DiscoverySchool.com lesson plan library for grades 6-8. It focuses on the ecology of the Grand Canyon area. Students act as scientists investigating the damming of the Colorado River by the Glen Canyon dam and experimental flooding that took place in 1996. They then write a proposal as to whether or not more experimental flooding should be done on the area considering the ecological effects. It includes objectives, materials, procedures, discussion questions, evaluation ideas, extensions, suggested readings, and vocabulary. There are videos available to order which complement this lesson, an audio-enhanced vocabulary list, and links to teaching tools for making custom quizzes, worksheets, puzzles and lesson plans.

231

Ancient Observatories: Chaco Canyon  

NSDL National Science Digital Library

Located in the northwest corner of New Mexico, Chaco Canyon is a shallow, ten-mile canyon accessible only by washboard dirt roads. It is an area of tremendous cultural importance, as it was once the center of an elaborate system of buildings, roadways, and other construction. Intense building activity continued at the site until about AD 1150, and then it was quickly abandoned. Today, it is a National Historic Park and a UNESCO World Heritage Site. On this site created by the Exploratorium in San Francisco, visitors can learn about this unique place via sections that provide insight into its layout, its history of human habitation, and also its various celestial alignments. First-time visitors can click on the Sense of Place tab to view a time-lapse video of the site. The Time area is remarkable, as visitors can read an essay titled "How Old Is It?" and then watch "Migration Stories," which talks about the experiences that humans have had there over the centuries. The site is rounded out by the Observation area, which allows users to learn about how the canyon's unique qualities have fascinated visitors, explorers, and others.

232

Submarine ramp facies model for delta-fed, sand-rich turbidite systems  

SciTech Connect

Some sandy turbidite successions contain facies that differ in significant ways from those predicted by the canyonfed submarine fan depositional model. The key differences are the absence of a master slope channel or canyon through which sediment is transported to the basin, and the lack of facies segregation into distinct channel and overbank or interchannel facies associations within the turbidite sequence. These types of sequences can be better described using a delta-fed submarine ramp depositional model. The primary components of this model are: a sandy deltaic system that has prograded to the shelf-slope break; an abbreviated section of mud-rich slope deposits traversed by multiple shallow channels that transport sand from the delta front to the deeper basin; very sandy proximal ramp deposits composed dominantly of laterally continuous sheets of Facies B turbidites; and less sandy distal ramp deposits characterized by an increase in the abundance of Facies C and D turbidites. Ramp turbidites characteristically display statistically random patterns of bed thickness. Submarine ramp development requires rapid sediment accumulation (>800 ft or 250 m/m.y.) in turbidite basins of shallow to moderate depth where deltaic progradation is rapid enough to mask the structural relief along basin margins. The delta-fed submarine ramp facies model may be useful in describing short-lived sandy depositonal episodes in some rapidly aggrading and prograding basinal sequences. As such, they represent one member in a spectrum of submarine fan depositional styles.

Heller, P.L.; Dickinson, W.R.

1985-06-01

233

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

234

Obstacle avoidance sonar for submarines  

Microsoft Academic Search

The Advanced Mine Detection Sonar (AMDS) system was designed to operate in poor environments with high biological and\\/or shallow-water boundary conditions. It provides increased capability for active detection of volume, close-tethered, and bottom mines, as well as submarine and surface target active\\/passive detection for ASW and collision avoidance. It also provides bottom topography mapping capability for precise submarine navigation in

Albert C. Dugas; Kenneth M. Webman

2002-01-01

235

Computer simulation of submarine motion  

E-print Network

COMPUTER SIMULATION OF SUBMARINE MOTION A Thesis by JEFFERY ALAN ZURFLUEH Submitted to the Office of Graduate Studies of Texas A&M University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE May 1991 Major... Subject: Mechanical Engineering COMPUTER SIMULATION OF SUBMARINE MOTION A Thesis by JEFFERY ALAN ZURFLUEH Approved as to style and content by: Make McDermott, Jr. ( Chair of Committee ) Glen Williams ( Member ) Lo 4verett ( Member ) gu r Walter...

Zurflueh, Jeffery Alan

1991-01-01

236

Sunset over Red Rock Canyon  

USGS Multimedia Gallery

Pine Creek Canyon is a remnant ecosystem of loblolly pines. A remnant ecosystem is the last vestige of an ecosystem type that used to be more widespred. Red Rock Canyon is a National Conservation Area managed by the Bureau of Land Management, located just outside of Las Vegas, Nevada. It is part of...

237

Yucca in Pine Creek Canyon  

USGS Multimedia Gallery

Pine Creek Canyon is a remnant ecosystem of loblolly pines. A remnant ecosystem is the last vestige of an ecosystem type that used to be more widespred. Red Rock Canyon is a National Conservation Area managed by the Bureau of Land Management, located just outside of Las Vegas, Nevada. It is part of...

238

Sunset in Pine Creek Canyon  

USGS Multimedia Gallery

Pine Creek Canyon is a remnant ecosystem of loblolly pines. A remnant ecosystem is the last vestige of an ecosystem type that used to be more widespred. Red Rock Canyon is a National Conservation Area managed by the Bureau of Land Management, located just outside of Las Vegas, Nevada. It is part of...

239

Yuccas in Pine Creek Canyon  

USGS Multimedia Gallery

The Mojave Desert, home to drought-tolerant plants like yuccas, gradually mixes with loblolly pine ecosystems in Pine Creek Canyon. Pine Creek Canyon is a remnant ecosystem of loblolly pines. A remnant ecosystem is the last vestige of an ecosystem type that used to be more widespred. Red Rock Cany...

240

Chollas in Pine Creek Canyon  

USGS Multimedia Gallery

The Mojave Desert, home to drought-tolerant plants like Cholla cacti, gradually mixes with loblolly pine ecosystems in Pine Creek Canyon. Pine Creek Canyon is a remnant ecosystem of loblolly pines. A remnant ecosystem is the last vestige of an ecosystem type that used to be more widespred. Red Roc...

241

Manzanita in Pine Creek Canyon  

USGS Multimedia Gallery

Pine Creek Canyon is a remnant ecosystem of loblolly pines. A remnant ecosystem is the last vestige of an ecosystem type that used to be more widespred. Red Rock Canyon is a National Conservation Area managed by the Bureau of Land Management, located just outside of Las Vegas, Nevada. It is part of...

242

Cedar Forests of Bryce Canyon  

USGS Multimedia Gallery

Bryce Canyon is a unique sandstone formation in southern Utah. It is home to a large number of hoodoos, which are oddly shaped pillars of rock that formed due to different erosion rates for the dolomite that caps them and the sandstone that forms their base. Bryce Canyon is also home to large numbe...

243

Snow-covered Bryce Canyon  

USGS Multimedia Gallery

Bryce Canyon is a unique sandstone formation in southern Utah. It is home to a large number of hoodoos, which are oddly shaped pillars of rock that formed due to different erosion rates for the dolomite that caps them and the sandstone that forms their base. Bryce Canyon is also home to large numbe...

244

Bryce Canyon Wall of Windows  

USGS Multimedia Gallery

Bryce Canyon's Wall of Windows, a series of sandstone arches and hoodoos in the Bryce Amphitheater. Bryce Canyon is a unique sandstone formation in southern Utah. It is home to a large number of hoodoos, which are oddly shaped pillars of rock that formed due to different erosion rates for the dolom...

245

Rainbow Point of Bryce Canyon  

USGS Multimedia Gallery

View of Bryce Canyon National Park from Rainbow Point. In the foreground are sandstone hoodoos. Bryce Canyon is a unique sandstone formation in southern Utah. It is home to a large number of hoodoos, which are oddly shaped pillars of rock that formed due to different erosion rates for the dolomite ...

246

Cedar Tree in Bryce Canyon  

USGS Multimedia Gallery

A cedar tree in Bryce Canyon National Park. Bryce Canyon is a unique sandstone formation in southern Utah. It is home to a large number of hoodoos, which are oddly shaped pillars of rock that formed due to different erosion rates for the dolomite that caps them and the sandstone that forms their ba...

247

Bryce Canyon's Navajo Loop Trail  

USGS Multimedia Gallery

Views along the Navajo Loop Trail in Bryce Canyon National Park. Bryce Canyon is a unique sandstone formation in southern Utah. It is home to a large number of hoodoos, which are oddly shaped pillars of rock that formed due to different erosion rates for the dolomite that caps them and the sandston...

248

Rainbow Point of Bryce Canyon  

USGS Multimedia Gallery

View of Bryce Canyon National Park from Rainbow Point. In the foreground are sandstone hoodoos and in the background is the Grand Staircase-Escalante National Monument, which is managed by the Bureau of Land Management. Bryce Canyon is a unique sandstone formation in southern Utah. It is home to a ...

249

Bryce Canyon's Wall of Windows  

USGS Multimedia Gallery

Bryce Canyon's Wall of Windows, a series of sandstone arches and hoodoos in the Bryce Amphitheater. Bryce Canyon is a unique sandstone formation in southern Utah. It is home to a large number of hoodoos, which are oddly shaped pillars of rock that formed due to different erosion rates for the dolom...

250

Cedar Forest in Bryce Canyon  

USGS Multimedia Gallery

A cedar forest in Bryce Canyon National Park, viewed from Rainbow Point. Bryce Canyon is a unique sandstone formation in southern Utah. It is home to a large number of hoodoos, which are oddly shaped pillars of rock that formed due to different erosion rates for the dolomite that caps them and the ...

251

Cedar Valley in Bryce Canyon  

USGS Multimedia Gallery

Bryce Canyon is a unique sandstone formation in southern Utah. It is home to a large number of hoodoos, which are oddly shaped pillars of rock that formed due to different erosion rates for the dolomite that caps them and the sandstone that forms their base. Bryce Canyon is also home to large numbe...

252

Sunset over Pine Creek Canyon  

USGS Multimedia Gallery

Pine Creek Canyon is a remnant ecosystem of loblolly pines. A remnant ecosystem is the last vestige of an ecosystem type that used to be more widespred. Red Rock Canyon is a National Conservation Area managed by the Bureau of Land Management, located just outside of Las Vegas, Nevada. It is part of...

253

Submarine daylight and ecology  

Microsoft Academic Search

The different parameters acting upon daylight before it reaches underwater organisms are discussed. Methods for measuring these parameters are reviewed, and lightsensing units equipped with hemispherical collectors and possessing a narrow spectral sensitivity band are recommended for use in marine biology. A new formula relating Secchi-disk readings to attenuation coefficients is proposed. A method is suggested which makes it possible

S. Weinberg

1976-01-01

254

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

USGS Publications Warehouse

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

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

2012-01-01

255

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

256

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 of numerous submarine landslides in French Polynesia. This inventory shows an evolution of the landslide type with the age of oceanic islands. Submarine active volcanoes are subject to superficial landslides of fragmental

Clouard, Valerie

257

Submarine hydrothermal fossils confirmed  

NASA Astrophysics Data System (ADS)

Researchers from Princeton University (D. Crerrar et al, Econ. Geol., May 1982) have documented, in considerable detail, evidence for the formation of some of the 800 or more manganiferous chert deposits occurring in the central belt of the Fransiscan formation in northwestern California. They confirm the surprisingly old conclusion o f Tiaferro and Hudson (Cal. Div. Mines Bull., 125, 217-276, 1943) that the Fransiscan chert deposits probably represent the fossil remains of submarine hydrothermal vents.The deposits resemble recently discovered hydrothermal mounds near the Galapagos rift, the Gulf of Aden, and the Mid-Atlantic Ridge. As the Princeton investigators point out, there are important implications of the existence of deep hydrothermal circulation systems at oceanic spreading centers throughout geologic time. They note that the calculated annual flow of hydrothermal fluids in such processes is about 1017 g, which implies that the entire volume of the oceans could circulate completely every 10 million years. With such circulation, the hydrothermal processes along midocean ridges could control the composition of seawater and strongly influence the geochemical flux of elements in the marine environment.

Bell, Peter M.

258

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

259

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

260

Submarine Warfare in the A Bibliography  

E-print Network

Submarine Warfare in the 20th & 21st Centuries: A Bibliography Compiled by Michaele Lee Huygen 3D, 1966. p. 205. This bibliography is a revised edition of the bibliography Submarine Warfare in the 20th & 21st Centuries, 2003, which is in turn a revised and expanded version of Submarine Warfare in the 20

261

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.

Bob Ribokas

262

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

263

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, Bernard

2012-06-21

264

1996 Grand Canyon Flood Analysis  

NSDL National Science Digital Library

Mark Manone, Northern Arizona University Summary Analyze the effect of a 1996 controlled flood on a sandbar in Grand Canyon. This exercise uses Spatial Analyst and 3D Analyst Context Type and level of course ...

Mark Manone

265

Grand Canyon: The Hidden Secrets  

NSDL National Science Digital Library

Summertime means vacations for many people, and for many of these sojourning to the American Southwest, this may mean a trip to the brilliance that is the Grand Canyon in northern Arizona. The people at National Geographic certainly know this area quite well, as they have sponsored a number of research expeditions there over the past century or so. Designed as a way to publicize the film that the organization plays at their canyon visitor center, this site contains a number of helpful features for those persons who may be visiting the canyon. First, visitors will want to look at the interactive map of the South Rim offered here. The map allows visitors to learn about selected features of the area, such as the famous bald eagles, the various outlooks, and the plants indigenous to the region. The site also includes a section for young people, a number of free screensavers and wallpapers, along with a travel guide to visiting the Grand Canyon.

266

Canyon waste dump case study  

SciTech Connect

This data packet contains the Canyonville Canyon Waste Dump results of the various physical environmental sampling. Core samples were taken from the on site waste material. Vertical grab samples were made from these borings. The waste samples were screened fro volatile organic compounds (VOC) and logged for lithology. Soil samples were also tested for VOC. Composite sediment samples were taken using a coring device known as a clam gun. No surface water was available for testing from the intermittent Canyon Wash. The hydrogeology of the Canyon Waste Dump was inferred from lithologic logs and hydraulic data from the five monitoring wells located along the canyon floor. Groundwater was monitored through five wells. The soil vapor and air screening techniques used were adaptations of the EPA ERT and NIOSH methodologies. 4 figs., 9 tabs.

Land, M.D.; Brothers, R.R. (Tennessee Univ., Knoxville, TN (United States)); McGinn, C.W. (Oak Ridge National Lab., TN (United States))

1991-01-01

267

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

268

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

269

Mineral resources of the Desolation Canyon, Turtle Canyon, and Floy Canyon Wilderness Study Areas, Carbon Emery, and Grand counties, Utah  

SciTech Connect

This paper reports on the Desolation Canyon, Turtle Canyon, and Floy Canyon Wilderness Study Areas which include 242,000 acres, 33,690 acres, and 23,140 acres. Coal deposits underlie all three study areas. Coal zones in the Blackhawk and Nelsen formations have identified bituminous coal resources of 22 million short tons in the Desolation Canyon Study Area, 6.3 million short tons in the Turtle Canyon Study Area, and 45 million short tons in the Floy Canyon Study Area. In-place inferred oil shale resources are estimated to contain 60 million barrels in the northern part of the Desolation Canyon area. Minor occurrences of uranium have been found in the southeastern part of the Desolation Canyon area and in the western part of the Floy Canyon area. Mineral resource potential for the study areas is estimated to be for coal, high for all areas, for oil and gas, high for the northern tract of the Desolation Canyon area and moderate for all other tracts, for bituminous sandstone, high for the northern part of the Desolation Canyon area, and low for all other tracts, for oil shale, low in all areas, for uranium, moderate for the Floy Canyon area and the southeastern part of the Desolation Canyon area and low for the remainder of the areas, for metals other than uranium, bentonite, zeolites, and geothermal energy, low in all areas, and for coal-bed methane unknown in all three areas.

Cashion, W.B.; Kilburn, J.E.; Barton, H.N.; Kelley, K.D.; Kulik, D.M. (US Geological Survey (US)); McDonnell, J.R. (Bureau of Mines (US))

1990-09-01

270

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

271

Implications for the Removal of Invasive Species in Canyon de Chelly National Monument  

Microsoft Academic Search

As part of a study to investigate the causes of channel narrowing and incision in Canyon de Chelly National Monument, the effects of Tamarix and Russian-olive on streambank stability were evaluated. Root tensile strengths and distributions in streambanks were measured and used in combination in a root-reinforcement model to estimate the additional cohesion provided to layers of each streambank. Relations

A. Simon; N. Pollen; K. L. Jaeger; E. E. Wohl

2006-01-01

272

Possible Connections Between the Coronado Bank Fault Zone and the Newport-Inglewood, Rose Canyon, and Palos Verdes Fault Zones Offshore San Diego County, California.  

NASA Astrophysics Data System (ADS)

High-resolution multichannel seismic-reflection and deep-tow Huntec data collected by the USGS were interpreted to map the Coronado Bank fault zone (CBFZ) offshore San Diego County, California. The CBFZ is comprised of several major strands (eastern, central, western) that change in both orientation and degree of deformation along strike. Between Coronado Bank and San Diego, the CBFZ trends N25W and occupies a narrow 7 km zone. Immediately north of La Jolla submarine canyon (LJSC), the easternmost strand changes orientation to almost due north and appears to be offset in a right-lateral sense across the canyon axis. The strand merges with a prominent fault that follows the base of the continental slope in about 600 m water depth. The central portion of the CBFZ is mapped as a negative flower structure and deforms seafloor sediment as far north as 15 km north of LJSC. Farther north, this structure is buried by more than 400 m of basin sediment. Along the eastern edge of the Coronado Bank, the western portion of the CBFZ is characterized by high angle normal faults that dip to the east. North of the Coronado Bank, the western segment follows the western edge of a basement high; it cuts through horizontal basin reflectors and in places deforms the seafloor. We mapped an additional splay of the CBFZ that trends N40W; it is only observed north and west of LJSC. Although the predominant trend of the CBFZ is about N40W, along strike deviations from this orientation of some of the strands indicate that these strands connect with other offshore fault zones in the area. Based on the limited data available, the trend of the CBFZ south of Coronado Bank suggests that it might connect with the Rose Canyon fault zone (RCFZ) that has been mapped in San Diego Bay. North of Coronado Bank, the CBFZ is a much broader fault zone (about 25 km wide) composed of diverging fault strands. The westernmost strand may merge with the western strand of the Palos Verdes fault zone (PVFZ) south of Lasuen Knoll. The eastern strand trends toward the Newport-Inglewood fault zone (NIFZ) as imaged offshore near Dana Point. These connections suggest that the CBFZ is linked at depth with other prominent fault zones to the north (PVFZ and NIFZ) as well as to the south (RCFZ).

Sliter, R. W.; Ryan, H. F.

2003-12-01

273

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.

Dennis Dahms

274

Snake Hells Canyon Subbasin Management Plan  

E-print Network

Snake Hells Canyon Subbasin Management Plan May 2004 Prepared for the Northwest Power and Conservation Council Subbasin Team Leader Nez Perce Tribe Watershed Division Written by Ecovista #12;Snake...............................................................................8 4 VISION FOR THE SNAKE HELLS CANYON SUBBASIN

275

How Was the Grand Canyon Formed?  

NSDL National Science Digital Library

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

276

Sediment transport processes at the head of Halibut Canyon, Eastern Canada margin: An interplay between internal tides and dense shelf water cascading.  

NASA Astrophysics Data System (ADS)

To investigate the processes by which sediment is transported through a submarine canyon incised in a glaciated margin, the bottom boundary layer quadrapod RALPH was deployed at 276-m depth in the West Halibut Canyon (off Newfoundland) during winter 2008-2009. Two main sediment transport processes were identified throughout the deployment. Firstly, periodic increases of near-bottom suspended-sediment concentrations (SSC) were recorded associated with the up-canyon propagation of the semidiurnal internal tidal bore along the canyon axis, carrying fine sediment particles resuspended from deeper canyon regions. The recorded SSC peaks, lasting less than one hour, were observed sporadically and were linked to bottom intensified up-canyon flows concomitant with sharp drops in temperature. Secondly, sediment transport was also observed during events of intensified down-canyon current velocities that occurred during periods of sustained heat loss from surface waters, but were not associated with large storms. High-resolution velocity profiles throughout the water column during these events revealed that the highest current speeds (~1 m s-1) were centered several meters above the sea floor and corresponded to the region of maximum velocities of a gravity flow. Such flows had associated low SSC and cold water temperatures and have been interpreted as dense shelf water cascading events channelized along the canyon axis. Sediment transport during these events was largely restricted to bedload and saltation, producing winnowing of sands and fine sediments around larger gravel particles. Analysis of historical hydrographic data suggests that the origin of such gravity flows is not related to the formation of coastal dense waters advected towards the canyon head. Rather, the dense shelf waters appear to be generated around the outer shelf, where convection during winter is able to reach the sea floor and generate a pool of near-bottom dense water that cascades into the canyon during one or two tidal cycles. A similar transport mechanism can occur in other submarine canyons along the eastern Canadian margin, as well in other canyoned regions elsewhere, where winter convection generally reaches the shelf-edge.

Puig, Pere; Greenan, Blair J. W.; Li, Michael Z.; Prescott, Robert H.; Piper, David J. W.

2013-04-01

277

Geology Fieldnotes: Grand Canyon National Park, Arizona  

NSDL National Science Digital Library

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

278

32 CFR 707.7 - Submarine identification light.  

Code of Federal Regulations, 2010 CFR

...2010-07-01 false Submarine identification light. 707.7 Section 707.7 National Defense...WITH RESPECT TO ADDITIONAL STATION AND SIGNAL LIGHTS § 707.7 Submarine identification light. Submarines may display, as a...

2010-07-01

279

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

280

32 CFR 707.7 - Submarine identification light.  

Code of Federal Regulations, 2013 CFR

... 2013-07-01 2013-07-01 false Submarine identification light. 707.7 Section...ADDITIONAL STATION AND SIGNAL LIGHTS § 707.7 Submarine identification light. Submarines may display, as a distinctive...

2013-07-01

281

32 CFR 707.7 - Submarine identification light.  

Code of Federal Regulations, 2014 CFR

... 2014-07-01 2014-07-01 false Submarine identification light. 707.7 Section...ADDITIONAL STATION AND SIGNAL LIGHTS § 707.7 Submarine identification light. Submarines may display, as a distinctive...

2014-07-01

282

32 CFR 707.7 - Submarine identification light.  

Code of Federal Regulations, 2012 CFR

... 2012-07-01 2012-07-01 false Submarine identification light. 707.7 Section...ADDITIONAL STATION AND SIGNAL LIGHTS § 707.7 Submarine identification light. Submarines may display, as a distinctive...

2012-07-01

283

Submarines, spacecraft and exhaled breath.  

PubMed

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

Pleil, Joachim D; Hansel, Armin

2012-03-01

284

Russian nuclear-powered submarine decommissioning  

SciTech Connect

Russia is facing technical, economic and organizational difficulties in dismantling its oversized and unsafe fleet of nuclear powered submarines. The inability of Russia to deal effectively with the submarine decommissioning crisis increases the risk of environmental disaster and may hamper the implementation of the START I and START II treaties. This paper discusses the nuclear fleet support infrastructure, the problems of submarine decommissioning, and recommends international cooperation in addressing these problems.

Bukharin, O. [Princeton Univ., NJ (United States); Handler, J. [Greenpeace International`s Disarmament Campaign, Washington, DC (United States)

1995-11-01

285

Saga is largest commercial submarine ever  

SciTech Connect

The long-range autonomous submarine, Saga, went nuclear last year with an agreement between the French and two Canadian companies. The agreement to convert the prototype from Swedish Stirling closed-cycle combustion engines to a nuclear power supply will make Saga the first non-defense nuclear submarine. With an external hull displacement of 500 tons, Saga will be the largest commercial submarine ever built.

Not Available

1985-05-01

286

Tsunami Modeling from Submarine Landslides  

NSDL National Science Digital Library

This paper describes a kinematic model that computes tsunamis generated from submarine landslides. The model is based on bathymetric (ocean floor modeling) data and historical tsunami data. The papers' main focus is the application of the model to the 1741 Oshima-Oshima Tsunami in Japan and landslide events around the Hawaiian Islands. This paper was presented at the U.S. National Tsunami Hazard Mitigation Program Review and International Tsunami Symposium in Seattle, Washington on August 10, 2001.

Kenji Satake

287

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

288

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

289

Attributes and origins of ancient submarine slides and filled embayments: Examples from the Gulf Coast basin  

SciTech Connect

Large submarine slides and associated shelf margin embayments represent an intermediate member in the continuum of unstable shelf margin features. On seismic profiles, they may resemble submarine canyons, but are different in their size, morphology, origin, and hydrocarbon exploration potential. Two large Neogene submarine slides, located in the northwestern Gulf Coast Basin, formed on the upper slope and flanks of prominent shelf-margin deltas. The basal detachment surface of each slide is a structural discontinuity that may be misinterpreted as an erosional unconformity and misidentified as a stratigraphic boundary separating depositional sequences. Regional stratigraphic correlations indicate that both slides were initiated after the continental platform was flooded. The condensed sections deposited during the rise in relative sea level contain the basal detachment surfaces. The relationships between the slides and sea level fluctuations are uncertain. The shelf-margin embayments created by the slides apparently were partly excavated during periods of lowered relative sea level and were filled during sea level rise and highstand. Eventually the preslide morphology of the shelf margin was restored by coalsced prograding deltas. Submarine slides exhibit landward dipping, wavy, mounded, and chaotic seismic reflection that are manifestations of slump blocks and other mass transport material. Composition of these internally derived slide deposits depends on th composition of the pre-existing shelf margin. Embayment fill above the slide consists mostly of externally derived mudstones and sandstones deposited by various disorganized slope processes, as well as more organized submarine channel-level systems. Thickest slope sandstones, which are potential hydrocarbon reservoirs, commonly occur above the basal slide mudstones where seismic reflections change from chaotic patterns to overlying wavy or subhorizontal reflections. 46 refs., 10 figs., 1 tab.

Morton, R.A. (Univ. of Texas, Austin (United States))

1993-06-01

290

ewly discovered at the bottom of the Hudson Canyon, the largest submarine canyon off the eastern United States, is  

E-print Network

opportunity to enhance our PowerBuoy® wave-energy technology. Our collaboration brings to the marketplace an innovative New Jersey product offering." --Charles F. Dunleavy (RBS'74), CEO, Ocean Power Technologies Coastal Ocean Observation Catches the Next Wave Under development off the coast of New Jersey is a network

Garfunkel, Eric

291

Tubes at Glen Canyon Dam  

USGS Multimedia Gallery

The river outlet tubes at Glen Canyon Dam on the Colorado River in Arizona. At noon Monday, Nov. 19, U.S. Interior Secretary Ken Salazar will open the dam's river outlet tubes, releasing controlled flows larger than the usual 8,000-25,000 cubic feet per second that flows through the turbines of...

292

The canyon system on Mars  

NASA Technical Reports Server (NTRS)

Individual Martian equatorial troughs are described, and their stratigraphy, geomorphology and structure are discussed. Possible origins and the overall sequence of events are addressed. Wall rock, interior layered deposits, irregular floor deposits, fractured floor material, and surficial deposits are examined. Chasma walls, wall stability, pits and pit chains, tributary canyons, and the transition from troughs to channels are also discussed.

Lucchitta, B. K.; Mcewen, A. S.; Clow, G. D.; Geissler, P. E.; Singer, R. B.; Schultz, R. A.; Squyres, S. W.

1992-01-01

293

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

294

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

295

Topographic characteristics of the submarine Taiwan orogen  

NASA Astrophysics Data System (ADS)

A complete digital elevation and bathymetry model of Taiwan provides the opportunity to characterize the topography of an emerging mountain belt. The orogen appears to form a continuous wedge of constant slope extending from the subaerial peaks to the submarine basin. We compare submarine channel systems from the east coast of Taiwan with their subaerial counterparts and document a number of fundamental similarities between the two environments. The submarine channel systems form a dendritic network with distinct hillslopes and channels. There is minimal sediment input from the subaerial landscape and sea level changes are insignificant, suggesting that the submarine topography is sculpted by offshore processes alone. We implement a range of geomorphic criteria, widely applied to subaerial digital elevation models, and explore the erosional processes responsible for sculpting the submarine and subaerial environments. The headwaters of the submarine channels have steep, straight slopes and a low slope-area scaling exponent, reminiscent of subaerial headwaters that are dominated by bedrock landslides. The main trunk streams offshore have concave-up longitudinal profiles, extensive knickpoints, and a slope-area scaling exponent similar in form to the onshore fluvial domain. We compare the driving mechanisms of the likely offshore erosional processes, primarily debris flows and turbidity currents, with subaerial fluvial incision. The results have important implications for reading the geomorphic signals of the submarine and subaerial landscapes, for understanding the links between the onshore and offshore environments, and, more widely, for focusing the future research of the submarine slope.

Ramsey, L. A.; Hovius, N.; Lague, D.; Liu, C.-S.

2006-06-01

296

Direct measures of Submarine Groundwater Discharge (SGD)  

E-print Network

Page: 1 Direct measures of Submarine Groundwater Discharge (SGD) over a fractured rock aquifer of submarine groundwater discharge (SGD) have been made, but measurements along the South American coast and over fractured rock aquifers are especially rare. The rate and distribution of SGD was measured using

297

Submarine landslide geomorphology, US continental slope  

Microsoft Academic Search

The morphometric analysis of submarine landslides in four distinctly different tectonic environments on the continental slopes of Oregon, central California, Texas, and New Jersey provides useful insight into submarine process, including sediment transport mechanisms and slope stability. Using Geographic Information System (GIS) software, we identify landslides from multibeam bathymetric and GLORIA sidescan surveys based solely on surficial morphology and reflectivity.

B. g. Mcadoo; L. f. Pratson; D. l. Orange

2000-01-01

298

The role of upper-regime flow bedforms in the morphodynamics of submarine channels  

NASA Astrophysics Data System (ADS)

Advances in acoustic imaging of submarine canyons and channels have provided accurate renderings of seafloor geomorphology. Still, a fundamental understanding of channel inception, evolution, sediment transport, and the nature of the currents traversing these channels remains elusive. Here, we review a mosaic of geomorphology, shallow stratigraphy, and morphodynamics of channelized deep-water depositional systems of tectonically active slopes offshore of California, USA. These systems are imaged in high-resolution multi-beam sonar bathymetry (dominant frequency ~200 kHz) and seismic-reflection (2-16 kHz) data. From north to south, the Monterey East, Lucia Chica, and San Mateo channelized deep-water depositional systems show a breadth of geomorphology and stratigraphic architecture, including channel reaches of varying sinuosity, levees, terraces within channels, and crescent-shaped bedforms, especially in the thalwegs of incipient channel elements. Morphodynamic numerical modeling is combined with interpretations of seafloor and shallow subsurface stratigraphic imagery to demonstrate that the crescent-shaped bedforms common to channel thalwegs are likely to be cyclic steps. We propose that net-erosional and net-depositional cyclic steps play a fundamental role in the formation, filling, and maintenance phases of submarine channels in continental margins with high gradient, locally rugose bathymetry. These margins include passive-margin slopes subjected to gravity-driven tectonic deformation. In such settings, high gradients support the development of densimetric Froude-supercritical turbidity currents, and abrupt slope breaks can promote hydraulic jumps and the spontaneous evolution of an erodible seabed into cyclic steps. This morphodynamic investigation of turbidity currents and the seafloor has the potential to enhance prediction of the locations, stratigraphic evolution, and architecture of submarine canyon-channel systems.

Covault, Jacob A.; Kostic, Svetlana; Fildani, Andrea

2014-05-01

299

Carbonate apron models: Alternatives to the submarine fan model for paleoenvironmental analysis and hydrocarbon exploration  

USGS Publications Warehouse

Sediment gravity flow deposition along the deep-water flanks of carbonate platforms typically does not produce submarine fans. Rather, wedge-shaped carbonate aprons develop parallel to the adjacent shelf/slope break. The major difference between submarine fans and carbonate aprons is a point source with channelized sedimentation on fans, versus a line source with sheet-flow sedimentation on aprons. Two types of carbonate aprons may develop. Along relatively gentle (< 4??) platform-margin slopes, aprons form immediately adjacent to the shallow-water platform and are referred to as carbonate slope aprons. Along relatively steep (4-15??) platform margin slopes, redeposited limestones accumulate in a base-of-slope setting, by-passing an upper slope via a multitude of small submarine canyons, and are referred to as carbonate base-of-slope aprons. Both apron types are further subdivided into inner and outer facies belts. Inner apron sediments consist of thick, mud-supported conglomerates and megabreccias (Facies F) as well as thick, coarse-grained turbidites (Facies A) interbedded with subordinate amounts of fine-grained, peri-platform ooze (Facies G). Outer apron sediments consist of thinner, grain-supported conglomerates and turbidites (Facies A) as well as classical turbidites (Facies C) with recognizable Bouma divisions, interbedded with approximately equal proportions of peri-platform ooze (Facies G). Seaward, aprons grade laterally into basinal facies of thin, base-cut-out carbonate turbidites (Facies D) that are subordinate to peri-platform oozes (Facies G). Carbonate base-of-slope aprons grade shelfward into an upper slope facies of fine-grained peri-platform ooze (Facies G) cut by numerous small canyons that are filled with coarse debris, as well as intraformational truncation surfaces which result from submarine sliding. In contrast, slope aprons grade shelfward immediately into shoal-water, platform-margin facies without an intervening by-pass slope. The two carbonate apron models presented here offer alternatives to the submarine-fan model for paleoenvironmental analysis and hydrocarbon exploration for mass-transported carbonate facies. ?? 1986.

Mullins, H.T.; Cook, H.E.

1986-01-01

300

32. VIEW OF PHOTO CAPTIONED 'SUBMARINE BASE, NEW LONDON, CONN. ...  

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

32. VIEW OF PHOTO CAPTIONED 'SUBMARINE BASE, NEW LONDON, CONN. OCTOBER 3, 1932. COMPLETION OF ERECTION OF STEELWORK FOR ELEVATOR. 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

301

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

302

Mineral resources of the Coal Canyon, Spruce Canyon, and Flume Canyon Wilderness Study Areas, Grand county, Utah  

SciTech Connect

This paper reports on the Coal Canyon, Spruce Canyon, and Flume Canyon Wilderness Study Areas in the Book and Roan Cliffs in Grand Country, Utah, approximately 12 miles west of the Colorado state line. The wilderness study areas consist of a series of deep, stair-step-sided canyons and high ridges eroded into the flatlying sedimentary rocks of the Book Cliffs. Demonstrated coal reserves totaling 22,060,800 short tons and demonstrated subeconomic coal resources totaling 39,180,000 short tons are in the Coal Canyon Wilderness Study Area. Also, inferred subeconomic coal resources totaling 143,954,000 short tons are within the Coal Canyon Wilderness Study Area. No known deposits of industrial minerals are in any of the study area. All three of the wilderness study areas have a high resource potential for undiscovered deposits of coal and for undiscovered oil and gas.

Dickerson, R.P.; Gaccetta, J.D.; Kulik, D.M.; Kreidler, T.J.

1990-01-01

303

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

USGS Publications Warehouse

Six submarine slope canyons in an area of the northwestern Mediterranean, offshore from the Ebro River and Delta, were surveyed with bathymetric swathmapping (SeaBeam) and mid-range side-looking sonar (SeaMARC I). All of the canyons have slightly winding paths with concave-upwards gradients that are relatively steep shallower than 1,200 m. Two major types of canyons are identified on the basis of their morphologic character at the base of the slope; Type-I canyons lead to an unchannelled base-of-slope deposit and Type-II canyons are continuous with channel-levee systems that cross the rise. Four Type-I canyons were surveyed in the area. Two of these are broad, U-shaped, steep (average gradients of 1:14), do not indent the shelf, and terminate downslope at debris-flow deposits. These two canyons, the most northern in the area, have rounded heads with extensive gullies separated by knife-edge ridges. Relief of the canyon walls is about equal on both sides of the canyons, although the right-hand walls (looking downslope) are generally steeper. The other two Type-I canyons in the area are similar in that they do not indent the shelf, but they are much smaller and shallower and coalesce before terminating in the base-of-slope region. The two Type-II canyons that feed leveed-channels are U-shaped with flatter floors, longer profiles and gentler gradients than Type-I canyons. They are closer to the Valencia Valley and have relatively small cross-sectional areas. We propose a four-stage evolutionary sequence to explain the development of the canyons observed in this section on the prograding Ebro margin. During the initial stage, slumping and erosion on the slope creates a network of small gullies. During the next stage, headward growth of one (or more) gully leads to a major indentation of the shelf. This is the critical factor for developing a channel that will incise the slope and provide a major conduit for moving sediment to the basin. Stage 3 is characterized by the development of a continuous channel accompanied by levee growth across the lobe. In the final stage, the channel-levee system becomes inactive either through destruction by mass wasting, infilling of the channel, or loss of the major sediment source. ?? 1987.

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

1987-01-01

304

A study of sound absorption by street canyon boundaries and asphalt rubber concrete pavement  

NASA Astrophysics Data System (ADS)

A sound field model, based on a classical diffusion equation, is extended to account for sound absorption in a diffusion parameter used to model sound energy in a narrow street canyon. The model accounts for a single sound absorption coefficient, separate accommodation coefficients and a combination of separate absorption and accommodation coefficients from parallel canyon walls. The new expressions are compared to the original formula through numerical simulations to reveal the effect of absorption on sound diffusion. The newly established analytical formulae demonstrate satisfactory agreement with their predecessor under perfect reflection. As well, the influence of the extended diffusion parameter on normalized sound pressure levels in a narrow street canyon is in agreement with experimental data. The diffusion parameters are used to model sound energy density in a street canyon as a function of the sound absorption coefficient of the street canyon walls. The acoustic and material properties of conventional and asphalt rubber concrete (ARC) pavement are also studied to assess how the crumb rubber content influences sound absorption in street canyons. The porosity and absolute permeability of compacted specimens of asphalt rubber concrete are measured and compared to their normal and random incidence sound absorption coefficients as a function of crumb rubber content in the modified binder. Nonlinear trends are found between the sound absorption coefficients, porosity and absolute permeability of the compacted specimens and the percentage of crumb rubber in the modified binders. The cross-sectional areas of the air voids on the surfaces of the compacted specimens are measured using digital image processing techniques and a linear relationship is obtained between the average void area and crumb rubber content. The measured material properties are used to construct an empirical formula relating the average porosity, normal incidence noise reduction coefficients and percentage of crumb rubber in the modified binder of the compacted specimens.

Drysdale, Graeme Robert

305

Klettafjllin og Grand Canyon 1 Klettafjllin, Grand Canyon og Laramide byltingin  

E-print Network

Klettafjöllin og Grand Canyon 1 Klettafjöllin, Grand Canyon og Laramide byltingin Kristbjörg María farið í Colorado, vestan við Klettafjöllin, en þar er að finna hið mikilfenglega Grand Canyon sem sker. Myndun Klettafjallanna og Grand Canyon hefur lengi valdið miklum heilabrotum meðal vísindamanna, enda er

Ingólfsson, �lafur

306

36 CFR 7.92 - Bighorn Canyon National Recreation Area.  

Code of Federal Regulations, 2011 CFR

... Bighorn Canyon National Recreation Area. 7.92 Section... Bighorn Canyon National Recreation Area. (a) Aircraft-designated...in Bighorn Canyon National Recreation Area, except in the following...protection, and other management activities and objectives. [36...

2011-07-01

307

NOAA Explorations: Submarine Ring of Fire 2004  

NSDL National Science Digital Library

NOAA's 2004 Submarine Ring of Fire expedition's goals are to examine over a 1,000 km stretch of submarine volcanoes and sea-floor hot springs in the Mariana Island Arc. At this website, users can find general information about the Mariana Arc, the research, and the scientists involved. Educators can find intriguing lesson plans about volcanoes and the chemistry of hydrothermal vents for grades fifth through twelfth. The site presents fascinating materials about seafloor mapping, volcanism, and vent chemistry. Visitors can view amazing satellite images of the overall Mariana Arc Volcanic Chain, its sea floor, and the NW Uracas and Ahyi submarine volcanoes.

308

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

309

The submarine river of Port Miou (France), A karstic system inherited from the Messinian deep stage  

NASA Astrophysics Data System (ADS)

The Port Miou system (Cassis, France) is a two kilometers long submarine gallery that extends in the limestone series of Calanques (Marseille, France). The average discharge is between 2 to 5 m3/s but the water is brackish and cannot be used for water supply. In the 1970s, a dam was built to prevent saltwater intrusion in the cave but these experimental attempts did not succeed in getting rid of the residual salinity which remained near 3 g l-1 upstream the dam. The use of helium and later rebreathers by cave divers made possible the exploration of a vertical pit down to 179 m below the sea level. At that depth, the water is still brackish. The cave extends further and deeper but the exploration is limited by the present diving technology. The canyon of Cassidaigne is located a few kilometers south from Port Miou. It cuts the continental shelf where bathymetric studies have shown the presence of dolines. Caves and speleothems have been observed during submarine explorations on the walls of the canyon. This canyon is not connected to a continental valley and it is assumed that it is a pocket valley. Its presence is related to the several lowering stages of the Mediterranean Sea during the Messinian Salinity Crisis. We suggest that during the important drop of sea level of the Mediterranean, the underground river of Port-Miou, flowed several hundreds meters below its current position, and excavated the canyon. At the end of the Messinian crisis, the system was flooded by seawater. The karst water now flows through an upper gallery but the presence of a paleo-drain filled by seawater makes possible a deep marine intrusion into the karst system. Several geomorphologic clues (bathymetry, submarine valley network…) reinforce the fact that the continental shelf near Marseilles is an important karstic network drowned below the sea level. This model is supported by the observation in Port Miou of an important quantity of titanium at the upper surface of the cave sediment, upstream of the dam and at the end of the cave. The presence of heavy metals in the sediments of the Port Miou gallery is explained as resulting from the suction of residues of bauxite treatments, rejected in the nearby Cassidaigne deep-sea canyon at a depth of 300 m bsl. This residual product locally called "red mud" is very rich in titanium. The saline contamination of Port Miou could be carried out by a seawater inflow through a deep karstic conduit connected to the canyon of Cassidaigne. A long term monitoring of the springs, indicates that the system is contaminated by a permanent sweater inflow close to 500 l.s-1. A laboratory model has been realized that simulates perfectly the functioning.

Cavalera, T.; Gilli, E.

2009-04-01

310

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

311

Using Submarine Landslides to Predict Slope Stability  

NSDL National Science Digital Library

Students use detailed bathymetric maps to find submarine landslides and compare the slope of these slides to the slope of hills near school and home. By comparing the slopes they can consider slope failure, especially during earthquakes.

Shawn Doan

312

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

NASA Astrophysics Data System (ADS)

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

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

2012-11-01

313

Characterization of viscoelastic properties of submarine sediments  

E-print Network

CHARACTERIZATION OF VISCOELASTIC PROPERTIES OF SUBMARINE SEDIMENTS A Thesis by Jim Bob King Submitted to the Graduate College of Texas AAM University in partial fulfillment of the requirement for the degree of MASTER OF SCIENCE December... 1975 Major Subject: Civil Engineering CHARACTERIZATION OF VISCOELASTIC PROPERTIES OF SUBMARINE SEDIMENTS A Thesis by Jim Bob King Approved as to sty1e and content by: Chair an of Commi tee Head of Department Member Member December 1975...

King, Jim Bob

1975-01-01

314

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

315

Destabilization of streambanks by removal of invasive species in Canyon de Chelly National Monument, Arizona  

Microsoft Academic Search

As part of a study to investigate the causes of channel narrowing and incision in Canyon de Chelly National Monument, the effects of Tamarisk and Russian-olive on streambank stability were investigated. In this study, root tensile strengths and distributions in streambanks were measured and used in combination with a root-reinforcement model, RipRoot, to estimate the additional cohesion provided to layers

Natasha Pollen-Bankhead; Andrew Simon; Kristin Jaeger; Ellen Wohl

2009-01-01

316

Submarine landslides: processes, triggers and hazard prediction.  

PubMed

Huge landslides, mobilizing hundreds to thousands of km(3) of sediment and rock are ubiquitous in submarine settings ranging from the steepest volcanic island slopes to the gentlest muddy slopes of submarine deltas. Here, we summarize current knowledge of such landslides and the problems of assessing their hazard potential. The major hazards related to submarine landslides include destruction of seabed infrastructure, collapse of coastal areas into the sea and landslide-generated tsunamis. Most submarine slopes are inherently stable. Elevated pore pressures (leading to decreased frictional resistance to sliding) and specific weak layers within stratified sequences appear to be the key factors influencing landslide occurrence. Elevated pore pressures can result from normal depositional processes or from transient processes such as earthquake shaking; historical evidence suggests that the majority of large submarine landslides are triggered by earthquakes. Because of their tsunamigenic potential, ocean-island flank collapses and rockslides in fjords have been identified as the most dangerous of all landslide related hazards. Published models of ocean-island landslides mainly examine 'worst-case scenarios' that have a low probability of occurrence. Areas prone to submarine landsliding are relatively easy to identify, but we are still some way from being able to forecast individual events with precision. Monitoring of critical areas where landslides might be imminent and modelling landslide consequences so that appropriate mitigation strategies can be developed would appear to be areas where advances on current practice are possible. PMID:16844646

Masson, D G; Harbitz, C B; Wynn, R B; Pedersen, G; Løvholt, F

2006-08-15

317

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

318

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

319

Barrel Cactus in Pine Creek Canyon  

USGS Multimedia Gallery

Pine Creek Canyon is a remnant ecosystem of loblolly pines. A remnant ecosystem is the last vestige of an ecosystem type that used to be more widespred. Red Rock Canyon is a National Conservation Area managed by the Bureau of Land Management, located just outside of Las Vegas, Nevada. It is part of...

320

Sunset Panorama in Pine Creek Canyon  

USGS Multimedia Gallery

Pine Creek Canyon is a remnant ecosystem of loblolly pines. A remnant ecosystem is the last vestige of an ecosystem type that used to be more widespred. Red Rock Canyon is a National Conservation Area managed by the Bureau of Land Management, located just outside of Las Vegas, Nevada. It is part of...

321

Loblolly Pines in Pine Creek Canyon  

USGS Multimedia Gallery

Pine Creek Canyon is a remnant ecosystem of loblolly pines. A remnant ecosystem is the last vestige of an ecosystem type that used to be more widespred. Red Rock Canyon is a National Conservation Area managed by the Bureau of Land Management, located just outside of Las Vegas, Nevada. It is part of...

322

Snow-covered Sandstone at Bryce Canyon  

USGS Multimedia Gallery

Bryce Canyon is a unique sandstone formation in southern Utah. It is home to a large number of hoodoos, which are oddly shaped pillars of rock that formed due to different erosion rates for the dolomite that caps them and the sandstone that forms their base. Bryce Canyon is also home to large numbe...

323

Bryce Canyon and Grand Staircase-Escalante  

USGS Multimedia Gallery

Views along the Queen's Garden Trail in Bryce Canyon National Park; Grand Staircase-Escalante National Monument can be seen in the background. Bryce Canyon is a unique sandstone formation in southern Utah. It is home to a large number of hoodoos, which are oddly shaped pillars of rock that formed d...

324

Panorama of Bryce Canyon National Park  

USGS Multimedia Gallery

Bryce Canyon is a unique sandstone formation in southern Utah. It is home to a large number of hoodoos, which are oddly shaped pillars of rock that formed due to different erosion rates for the dolomite that caps them and the sandstone that forms their base. Bryce Canyon is also home to large numbe...

325

Bryce Canyon and Grand Staircase-Escalante  

USGS Multimedia Gallery

Bryce Canyon is a unique sandstone formation in southern Utah. It is home to a large number of hoodoos, which are oddly shaped pillars of rock that formed due to different erosion rates for the dolomite that caps them and the sandstone that forms their base. Bryce Canyon is also home to large numbe...

326

Big Canyon Creek Ecological Restoration Strategy  

Microsoft Academic Search

He-yey, Nez Perce for steelhead or rainbow trout (Oncorhynchus mykiss), are a culturally and ecologically significant resource within the Big Canyon Creek watershed; they are also part of the federally listed Snake River Basin Steelhead DPS. The majority of the Big Canyon Creek drainage is considered critical habitat for that DPS as well as for the federally listed Snake River

Lynn Rasmussen; Shannon Richardson

2007-01-01

327

Grand Canyon Monitoring and Research Center  

USGS Publications Warehouse

The Grand Canyon of the Colorado River, one of the world's most spectacular gorges, is a premier U.S. National Park and a World Heritage Site. The canyon supports a diverse array of distinctive plants and animals and contains cultural resources significant to the region's Native Americans. About 15 miles upstream of Grand Canyon National Park sits Glen Canyon Dam, completed in 1963, which created Lake Powell. The dam provides hydroelectric power for 200 wholesale customers in six western States, but it has also altered the Colorado River's flow, temperature, and sediment-carrying capacity. Over time this has resulted in beach erosion, invasion and expansion of nonnative species, and losses of native fish. Public concern about the effects of Glen Canyon Dam operations prompted the passage of the Grand Canyon Protection Act of 1992, which directs the Secretary of the Interior to operate the dam 'to protect, mitigate adverse impacts to, and improve values for which Grand Canyon National Park and Glen Canyon National Recreation Area were established...' This legislation also required the creation of a long-term monitoring and research program to provide information that could inform decisions related to dam operations and protection of downstream resources.

Hamill, John F.

2009-01-01

328

Comparing ecological restoration alternatives: Grand Canyon, Arizona  

Microsoft Academic Search

Three treatments designed to initiate the process of restoring the surface fire regime and open forest structure of a southwestern ponderosa pine forest were compared on the Kaibab National Forest along the Grand Canyon’s South Rim. The treatments were: (1) full restoration (FULL)—thinning trees to emulate stand structure prior to fire regime disruption ca. 1887, forest floor fuel treatment, and

Peter Z. Fulé; W. Wallace Covington; H. B. Smith; Judith D. Springer; Thomas A. Heinlein; Kristin D. Huisinga; Margaret M. Moore

2002-01-01

329

Human-Powered Submarine Competition: World Submarine International 1996 [and] Design Technology Exhibit: A School Model.  

ERIC Educational Resources Information Center

Hibbard describes the process used by students at Millersville University to build a human-powered submarine for entry in an international submarine competition. Edwards discusses the Design Technology Exhibit held at Lu Sutton Elementary School, the purpose of which was to challenge students to design a useful structure and provide them with the…

Hibberd, John C.; Edwards, Don

1996-01-01

330

The role of erosion by fish in shaping topography around Hudson submarine canyon.  

USGS Publications Warehouse

The close match of areas of rough topography and high tilefish populations, the active burrowing of the sea floor, and the clustered distribution of the burrows suggest that the hummocky topography in this area may be the result of continuous erosion by tilefish and associated crustaceans during the Holocene. -from Authors

Twichell, D.C.; Grimes, C.B.; Jones, R. S.; Able, K.W.

1985-01-01

331

Prehistoric deforestation at Chaco Canyon?  

PubMed Central

Ancient societies are often used to illustrate the potential problems stemming from unsustainable land-use practices because the past seems rife with examples of sociopolitical “collapse” associated with the exhaustion of finite resources. Just as frequently, and typically in response to such presentations, archaeologists and other specialists caution against seeking simple cause-and effect-relationships in the complex data that comprise the archaeological record. In this study we examine the famous case of Chaco Canyon, New Mexico, during the Bonito Phase (ca. AD 860–1140), which has become a prominent popular illustration of ecological and social catastrophe attributed to deforestation. We conclude that there is no substantive evidence for deforestation at Chaco and no obvious indications that the depopulation of the canyon in the 13th century was caused by any specific cultural practices or natural events. Clearly there was a reason why these farming people eventually moved elsewhere, but the archaeological record has not yet produced compelling empirical evidence for what that reason might have been. Until such evidence appears, the legacy of Ancestral Pueblo society in Chaco should not be used as a cautionary story about socioeconomic failures in the modern world. PMID:25071220

Wills, W. H.; Drake, Brandon L.; Dorshow, Wetherbee B.

2014-01-01

332

Prehistoric deforestation at Chaco Canyon?  

PubMed

Ancient societies are often used to illustrate the potential problems stemming from unsustainable land-use practices because the past seems rife with examples of sociopolitical "collapse" associated with the exhaustion of finite resources. Just as frequently, and typically in response to such presentations, archaeologists and other specialists caution against seeking simple cause-and effect-relationships in the complex data that comprise the archaeological record. In this study we examine the famous case of Chaco Canyon, New Mexico, during the Bonito Phase (ca. AD 860-1140), which has become a prominent popular illustration of ecological and social catastrophe attributed to deforestation. We conclude that there is no substantive evidence for deforestation at Chaco and no obvious indications that the depopulation of the canyon in the 13th century was caused by any specific cultural practices or natural events. Clearly there was a reason why these farming people eventually moved elsewhere, but the archaeological record has not yet produced compelling empirical evidence for what that reason might have been. Until such evidence appears, the legacy of Ancestral Pueblo society in Chaco should not be used as a cautionary story about socioeconomic failures in the modern world. PMID:25071220

Wills, W H; Drake, Brandon L; Dorshow, Wetherbee B

2014-08-12

333

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 draft Snake Hells Canyon Subbasin Assessment and Snake Hells Canyon Subbasin Management Plan prepared species in the Snake Hells Canyon subbasin. Section II summarizes the prioritization of these limiting

334

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

335

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

336

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

337

Predictability of Turbulent Flow in Street Canyons  

NASA Astrophysics Data System (ADS)

Although predictability is a subject of great importance in atmospheric modelling, there has been little research on urban boundary-layer flows. Here the predictability of street-canyon flow is examined numerically via large-eddy simulation of a unit-aspect-ratio canyon and neutrally stratified atmosphere. In spectral space there is indication of cascade-like behaviour away from the canyon at early times, but the error growth is essentially independent of scale inside the canyon; in physical space the error field is rather inhomogeneous and shows clear differences among the canyon, shear layer and inertial sublayer. The error growth is largely driven by the shear layer: errors generated above roof level are advected into the canyon while contributions from intermittent bursting and in situ development within the canyon play a relatively minor role. This work highlights differences between the predictability of urban flows and canonical turbulent flows and should be useful in developing modelling strategies for more realistic time-dependent urban flows.

Lo, K. W.; Ngan, K.

2015-03-01

338

Rapid canyon formation by extreme floods  

NASA Astrophysics Data System (ADS)

The formation of river gorges generally occurs over geomorphic timescales, with rates of river incision into bedrock infrequently exceeding millimeters per year. This is in contrast to relatively rare examples of bedrock canyons that have been cut in a matter of days or weeks by catastrophic floods. Here we report on several case studies of canyons inferred to have been cut by large magnitude, short-lived flood events. Canyon Lake Gorge, Texas, was cut ~ 10 m into jointed bedrock during a three-day historic flood event, illustrating that short lived floods can efficiently mobilize and transport large quantities of rock. New cosmogenic exposure dating of multiple features at Malad Gorge, Idaho, indicates that it was formed ~ 48 ka, equivalent to the age of Box Canyon located 18 km to the south, suggesting that flooding there was regional in scale. In all cases, we attribute extremely rapid canyon erosion (i.e., meters per day) to the dominance of plucking and toppling of jointed rock rather than the relatively slow process of fluvial abrasion. Large magnitude flows are inferred from the threshold required to topple blocks and transport boulders. The lack of upstream drainage-network development and the lack of fluvial abrasion features indicate the floods must have been short-lived. Canyons cut into plateau terrain by large magnitude, short duration floods appear to have distinctive morphologies including steep canyon headwalls with semi-circular planforms, suggesting flow focusing and toppling at the headwall, despite the largely flat initial topography. In contrast, neighboring canyons undergoing active fluvial abrasion tend to show potholes, polished and fluted rock, headwalls that are pointed in planform, and more gradual knickzones extending into well-developed drainage networks upstream. Modeling suggests that the rate of canyon cutting by large-scale floods in jointed rock may be limited only by the sediment transport capacity of the flow.

Lamb, M. P.; Mackey, B. H.; Lapotre, M. G.

2012-12-01

339

The Grand Canyon: How It Formed  

NSDL National Science Digital Library

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

340

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

341

WHAT TO DO WITH THE NUCLEAR SUBMARINES WITH DAMAGED CORES?  

Microsoft Academic Search

Some of the early nuclear submarines of Russia suffered accidents, e.g. criticality accidents or LOCAs, whereby the fuel assemblies of the reactor core were damaged and radioactive material released. In the 1960es the reactor compartment of such submarines was disposed of by cutting it out of the submarine and sinking it in the sea. However, since Russia became party to

P. L. OLGAARD; Olgaard Consult

342

Reducing Unsteady Loads on a Piggyback Miniature Submarine  

NASA Technical Reports Server (NTRS)

A small, simple fixture has been found to be highly effective in reducing destructive unsteady hydrodynamic loads on a miniature submarine that is attached in piggyback fashion to the top of a larger, nuclear-powered, host submarine. The fixture, denoted compact ramp, can be installed with minimal structural modification, and the use of it does not entail any change in submarine operations.

Lin, John

2009-01-01

343

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

344

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

345

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

346

32 CFR 700.1058 - Command of a submarine.  

Code of Federal Regulations, 2013 CFR

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

2013-07-01

347

On the frontal dynamics and morphology of submarine debris flows  

E-print Network

On the frontal dynamics and morphology of submarine debris flows Trygve Ilstada,*, Fabio V. De, MN 55414, USA Accepted 30 September 2004 Abstract Several submarine debris flows show an apparently reserved. Keywords: submarine slide; debris flow; Morphology; outrunner blocks; experiment 1. Introduction

348

32 CFR 700.1058 - Command of a submarine.  

Code of Federal Regulations, 2014 CFR

... 2014-07-01 false Command of a submarine. 700.1058 Section 700.1058 National...Detail to Duty § 700.1058 Command of a submarine. The officer detailed to command a submarine shall be an officer of the line in...

2014-07-01

349

32 CFR 700.1058 - Command of a submarine.  

Code of Federal Regulations, 2011 CFR

... 2011-07-01 false Command of a submarine. 700.1058 Section 700.1058 National...Detail to Duty § 700.1058 Command of a submarine. The officer detailed to command a submarine shall be an officer of the line in...

2011-07-01

350

Numerical simulation of tsunami waves generated by deformable submarine landslides  

E-print Network

Numerical simulation of tsunami waves generated by deformable submarine landslides Gangfeng Ma a 2013 Accepted 4 July 2013 Available online 15 July 2013 Keywords: Submarine landslide Nonhydrostatic wave model Tsunami wave Numerical modeling a b s t r a c t This paper presents a new submarine

Kirby, James T.

351

32 CFR 700.1058 - Command of a submarine.  

Code of Federal Regulations, 2012 CFR

... 2012-07-01 false Command of a submarine. 700.1058 Section 700.1058 National...Detail to Duty § 700.1058 Command of a submarine. The officer detailed to command a submarine shall be an officer of the line in...

2012-07-01

352

Tidal Conversion at a Submarine Ridge FRANOIS PTRLIS  

E-print Network

Tidal Conversion at a Submarine Ridge FRANÇOIS PÉTRÉLIS Laboratoire de Physique Statistique, Ecole-dimensional submarine ridge is computed using an integral-equation method. The problem is characterized by two tide over submarine topography is a main source of the mechanical energy required to power the internal

Young, William R.

353

Submarine Floating Antenna Model for LORAN-C Signal  

E-print Network

Submarine Floating Antenna Model for LORAN-C Signal Processing A. MONIN LAAS-CNRS France An electromagnetic model of the floating antenna used by submarines for LORAN-C radionavigation and very low The antenna used by submarines, for LORAN-C radionavigation and very low frequency (VLF) communications

Monin, André

354

Deep submarine pyroclastic eruptions: theory and predicted landforms and deposits  

E-print Network

Deep submarine pyroclastic eruptions: theory and predicted landforms and deposits James W. Head III October 2001; received in revised form 19 August 2002; accepted 19 August 2002 Abstract Submarine and illustrate the full range of submarine eruption styles, we model several possible scenarios for the ascent

Head III, James William

355

32 CFR 700.1058 - Command of a submarine.  

Code of Federal Regulations, 2010 CFR

... 2010-07-01 false Command of a submarine. 700.1058 Section 700.1058 National...Detail to Duty § 700.1058 Command of a submarine. The officer detailed to command a submarine shall be an officer of the line in...

2010-07-01

356

Introduction Deep-sea deposits from submarine landslides, debris  

E-print Network

Introduction Deep-sea deposits from submarine landslides, debris flows, and turbidity currents have with submarine mass-wasting. An example is the Storegga landslide on the Norwegian margin, which occurred about 9 detached from the front of slowing-down submarine landslides. With a runout ratio of the order 0

357

The relation between earthquakes, faulting, and submarine hydrothermal mineralization  

Microsoft Academic Search

Although the relationship between submarine hydrothermal activity and earthquakes was recognized over 20 years ago, it has still not been precisely defined. Faulting and permeability control fluid flow in the oceanic crust and therefore submarine hydrothermal activity at mid?ocean ridges. Microearthquakes associated with submarine hydrothermal activity tend to be small in magnitude and occur in swarms. Swarms of microearthquakes associated

G. P. Glasby

1998-01-01

358

Multidisciplinary Investigations of Submarine Flow to Biscayne Bay, Florida  

NASA Astrophysics Data System (ADS)

Biscayne Bay and Biscayne National Park (BNP) are located next to the Miami-Dade urban complex and are adjacent to the Dade County South Dade Landfill Facility and the Miami-Dade Water and Sewer South District Plant. The base of the landfill is lined to separate it from the underlying Miami Limestone, the host rock for the surficial Biscayne Aquifer. The sewage-treatment facility injects treated sewage into the lower Florida Aquifer (750 m) that is overlain by an aquitard termed the Middle Confining Unit (450 m). The Biscayne Aquifer (up to 50 m thick) borders the western margin of BNP, and the Floridan Aquifer underlies the entire park. There is concern about leakage of contaminated aquifer water into BNP and its potential effects on water quality. Groundwater flux to Biscayne Bay is being studied using pressure measurements and geochemical analyses from submarine wells, electromagnetic seepage meters, streaming resistivity profiling, and local and regional model simulations. Both seepage meters and water analyses provide point information that can be placed into the regional context provided by flow models and geochemical and geophysical profiling, which, in turn, constrain the groundwater contribution. Water samples were collected approximately quarterly from August 2002 until March 2004 from submarine wells along a transect through Biscayne Bay and across the reef to the shelf edge. Samples were analyzed for conductivity (salinity), dissolved oxygen, temperature, redox potential, nutrients, metals, strontium isotopes, radon, sulfate, and wastewater compounds. Low-salinity water was identified from nearshore wells and indicates seepage from the Biscayne Aquifer and/or surface-water intrusion into the rocks along western Biscayne Bay. Analyses of water samples (n = 109) collected from wells across the Florida shelf show no consistent evidence of wastewater contaminants occurring in groundwater beneath BNP. No significant leakage from the Floridan Aquifer (characterized by low strontium-isotope ratios) was detected in the wells. The groundwater beneath the shelf can be characterized as reduced seawater, modified by microbial respiration to remove oxygen, and interacting with sediments and minerals in the host limestone. The data from submarine well samples are consistent with groundwater model results that indicate a narrow zone of discharge along the western margin of Biscayne Bay. This zone varies in width from 100 to 1000 m along the coast. A seepage meter placed in this zone during March 2004 recorded an average flow of 23 cm/day. Submarine discharge is estimated to be about 6% of the surface-water flow to Biscayne Bay, and almost all of this is in the northern half of the bay, where shoreline and water-table elevations are greatest. Saltwater intrusion extends farther inland in the southern portion of the bay, where water-table and coastal elevations are low. Shoreline-parallel radon-222 profiles also indicate more seepage in the north than south, but suggest low-salinity water extends between 1 and 2 km offshore. Resistivity profiling provided a fourth technique (along with wells, models, and radon) that documents low-salinity water along the coast, particularly toward the northern bay. Resistivity is the only methodology that indicates presence of brackish water 5 km offshore, an observation that requires verification. Interdisciplinary approaches that estimate submarine flow to this tropical estuary are helping reinforce observations made by complimentary methods, while clearly identifying other observations as worthy of further investigation and verification.

Halley, R. B.; Reich, C. D.; Swarzenski, P. W.; Langevin, C. D.

2005-05-01

359

Observations of Seafloor Outcrops in the Oblique Subduction Setting of Adak Canyon: Implications for Understanding the Early History of the Aleutian Island Arc  

NASA Astrophysics Data System (ADS)

Submarine canyons in the western Aleutians (west of 177°W) are formed by oblique subduction, which has broken crustal blocks away from the arc massif and rotated them in clockwise sense, resulting in the formation of triangular-shaped summit basins and deep, structurally controlled submarine canyons (Geist et al., Tectonics v7, p327, 1988). A series of dives with the ROV Jason II on July 28-30, 2004 on Adak Canyon has provided the first-ever view of seafloor outcrops in an Aleutian canyon formed by this process. Two dives on the canyon's steep eastern wall revealed extensive exposures of blocky outcrops of volcanic rock at depths of 2900-1500 m. Samples of these units collected by the Jason II are a mixture of dark, pyroxene and plagioclase-phyric lavas and volcaniclastics. Degree of weathering/alteration is highly variable but some samples appear fresh. We anticipate that these rocks are offshore-equivalents of the Finger Bay Volcanics, which represent the earliest phase of Aleutian volcanism exposed on nearby Adak Island (e.g., Coats, 1956, USGS Bull. 1028-C). Exposures of granitic rock in Adak Canyon form low ledges of exfoliating outcrop interspersed with spheroidally weathered, bouldery sub-crop, in the depth range of 1800-1600 meters. Obtaining in-situ samples from these massive and subrounded exposures was not possible with the Jason II, but recovery of large, sub-angular slabs that litter the surface included samples of fresh diorite, fine-grained felsic intrusives and hydrothermally altered volcanic country rock. The stratigraphically highest exposures observed in Adak Canyon are gently dipping, poorly lithified `Middle Series' sedimentary rocks of probable Miocene-Oligocene age. All outcrop surfaces in Adak Canyon are covered with a uniformly dark brown, opaque coating of Mn oxide less than 1mm thick. Well-rounded cobbles and boulders interpreted to be glacial drift are largely free of Mn oxide coatings. Thick pavements of Mn-oxide were not observed. These observations indicate that combined seismic and dredging-geochemical studies will be a successful approach to unraveling the complete magmatic and tectonic history of the Aleutian arc crust, which due to the absence of significant arc-parallel rifting and backarc spreading remains largely intact and available for study. Dating and geochemical analysis of samples recovered on the July '04 Jason II expedition will provide a much-improved view of early Aleutian history.

Yogodzinski, G.; Scholl, D.; Jicha, B.; Wyatt, C.; Singer, B.; Kelemen, P.

2004-12-01

360

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

361

Saturation diving as a submarine rescue tool.  

PubMed

The U.S. Navy Submarine Rescue Diving and Recompression System (SRDRS) uses saturation diving to provide human intervention at the hatch of a disabled submarine. The system incorporates the basic elements of traditional saturation diving platforms to provide life support to divers at the worksite as well as in a decompression chamber in between work assignments. The demands of the submarine rescue mission require that the system provide quick response to an emergency virtually anywhere in the world. To answer these demands, SRDRS uses a mixture of state-of-the-art diving technologies and traditional approaches to life support in a quickly mobilized, easily transportable diving system capable of operating in extremely harsh environments. PMID:11538562

Johnson, J M

1996-01-01

362

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

363

DAM AND GEOMORPHOLOGICAL INFLUENCES ON COLORADO RIVER WATERBIRD DISTRIBUTION, GRAND CANYON, ARIZONA,  

E-print Network

Impoundment effects override natural, reach-based channel geomorphology influences on seasonal waterbird distribution in Grand Canyon along the Colorado River downstream from Glen Canyon Dam. Large winter waterbird populations were rare or non-existent prior to completion of Glen Canyon Dam in 1963, and pre-dam summer breeding was rare. Post-dam river corridor surveys of 13 geomorphological reaches from 1973 to 1994 detected 58 species of waterfowl, waders, shorebirds and piscivorous raptors, with a grand mean of 1382 waterbirds=reach (SE 310, n 727 reach surveys), and a mean area-adjusted rate of encounter (AARE) of 3728 waterbirds kmÿ1 hÿ1 of observation per reach (SE 691). The post-dam assemblage has been dominated by Anseriformes (13 diving and 12 dabbling species) and includes regionally significant populations of wintering waterfowl and bald eagle, and breeding mallard. Most wading birds and shorebirds occur primarily as migrants or summer vagrants. Total waterbird AARE was greatest in the productive clear water (CW) and variably turbid (VT) segments upstream from the Little Colorado River (LCR) (km 98), decreasing downstream on the usually turbid (UT) lower Grand Canyon segment. Mean total winter waterfowl AARE was 10768, and decreased by three orders of magnitude from the CW to the UT segments (p 00001). Mean total summer AARE was 27, and also decreased across the turbidity segments (p 0066). In contrast, AARE varied little between wide and narrow geomorphological reaches. Total AARE was only 14 and 13-fold greater in

unknown authors

364

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

365

Transporting submarine engines to power the PRT  

NASA Technical Reports Server (NTRS)

The city of Hampton was unable to supply adequate electric power to operate the PRT. Navy Captain Walter S. Diehl, Bureau of Aeronautics, acquired two 1000 hp submarine engines which were to be disposed of. BuAer 'loaned' the engines to the NACA, one of which is shown here. Next to the engine is Donald H. Wood, a mechanical engineer from Rensselaer Polytechnic Institute and Fred Weick's assistant. Propeller Research Tunnel (PRT) engineer Donald H. Wood ponders the unlikely transfer of a submarine engine from rail car to NACA truck, May 1926. Two such diesel engines powered the PRT.

1926-01-01

366

The Kaena Ridge Submarine Rift Zone off Oahu, Hawaii  

NASA Astrophysics Data System (ADS)

Deep-water multibeam data was collected in the Kauai Channel between the islands of Kauai and Oahu during the years 2000 to 2002 using the R/V Roger Revelle in support of the NSF funded Hawaii Ocean Mixing Experiment (HOME) with M. Gregg and A. Chave as principal investigators. The bathymetric surveys covered the Kaena Ridge, possibly a large submarine rift zone extension of the Waianae Volcano that makes up the western half of the island of Oahu. The Kaena ridge is bordered by the Kauai Channel and debris avalanche deposit material to the west, the Waianae slump to the south, and the Kaena slump to the north. The 35-55 km wide crest of the Kaena ridge extends 75-100 km northwest from Kaena Point, the westernmost tip of Oahu. The length and morphology resemble that of the Hana Ridge, the submarine extension of the Haleakala east rift zone. The broad central portion of Kaena ridge is comprised of two apparent lava shields 15 km and 10 km in diameter, both rising 200 m above the ridge (approximately 2500 m above the basal seafloor) to within 880 m and 660 m of sea level, respectively. The large size and distant location of the westernmost cone in the middle of the Kauai Channel suggests that it might predate Waianae Volcano and represent a precursor to the island of Oahu in the Hawaiian Chain, aborted before it ever reached sea level. Several 1500 m high steep concave landslide scars facing the giant Waianae slump mark the southern side of the ridge. To the north, a series of four 15 to 30 km wide benches step down to the basal seafloor, forming the Kaena slump, which may represent a less developed version of the Waianae slump. A 42 km long and 22 km wide (at its center) narrow rift zone ridge, in the classic Hawaiian submarine rift zone style (e.g., Puna ridge), bifurcates from the main broad ridge near the distal end. The smaller ridge trends north-northwest and is covered with approximately a dozen volcanic cones along its axis. Its rough morphology is characteristic of pillow and lobate lava flows effusing from a central dike injected rift zone.

Smith, J. R.

2002-12-01

367

77 FR 48151 - Boulder Canyon Project  

Federal Register 2010, 2011, 2012, 2013, 2014

...email jmurray@wapa.gov. SUPPLEMENTARY INFORMATION: Hoover Dam, authorized by the Boulder Canyon Project Act (45 Stat...Colorado River along the Arizona and Nevada border. Hoover Dam power plant has nineteen (19) generating units...

2012-08-13

368

Wintertime meteorology of the Grand Canyon region  

SciTech Connect

The Grand Canyon region of the American Southwest is an interesting region meteorologically, but because of its isolated location, the lack of major population centers in the region, and the high cost of meteorological field experiments, it has historically received little observational attention. In recent years, however, attention has been directed to episodes of visibility degradation in many of the US National parks, and two recent field studies focused on this visibility problem have greatly increased the meteorological data available for the Grand Canyon region. The most recent and comprehensive of these studies is the Navajo Generating Station Winter Visibility Study of 1989--90. This study investigated the sources of visibility degradation in Grand Canyon National Park and the meteorological mechanisms leading to low visibility episodes. In this paper we present analyses of this rich data set to gain a better understanding of the key wintertime meteorological features of the Grand Canyon region.

Whiteman, C.D.

1992-09-01

369

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

370

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

371

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

NASA Astrophysics Data System (ADS)

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

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

2009-12-01

372

Extremely Low Frequency (ELF) Communication to Submarines  

Microsoft Academic Search

An ELF (extremely low frequency) communication system has been proposed for communication from land to submerged submarines. We present an analytical study of conceptual feasibility of such a system and discuss some of its properties. We find no fundamental technical reason why such a system is infeasible. The present work yields the general structure of the receiver, and estimates for

HARRISON E. ROWE

1974-01-01

373

Morphology of Quench Crystals in Submarine Basalts  

Microsoft Academic Search

Submarine basalts from the mid-Atlantic ridge, Red Sea rift, and Joides site 105 in the western Atlantic have been studied in ultra thin, doubly polished thin sections. Most of the samples are pillow lava fragments containing a variety of skeletal crystal growth forms that can be related to three major textural zones in the pillows. Olivine appears as diffuse, lattice-like

Wilfred B. Bryan

1972-01-01

374

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

375

Character of submarine groundwater discharge around islands  

Microsoft Academic Search

Submarine groundwater discharge (SGD) from oceanic islands has been estimated to contribute over a third of the global SGD due to the high shoreline-to-land area ratio, orographic precipitation, short aquifer pathways and poorly developed surface drainage. Relatively few islands have been studied, but SGD is typically found to be an important, and often the only, source of nutrients to coastal

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

2009-01-01

376

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

377

Simulating the effects of Glen Canyon Dam releases on Grand Canyon river trips  

Microsoft Academic Search

The Shechter-Lucas wilderness use simulation model (WUSM) has been modified to quantify the effects of fluctuating Glen Canyon Dam releases on Grand Canyon river trips. The model now simulates changes in flow as predicted by the Streamflow Synthesis and Reservoir Regulation computer model for the Colorado River. This revised WUSM provides data on several flow-related effects, including delays at rapids,

Ronald E. Borkan; A. Heaton Underhill

1989-01-01

378

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

379

Experimental modeling of depositional turbidity currents in a sinuous submarine channel  

NASA Astrophysics Data System (ADS)

Submarine channels with intricate meandering patterns and extensive levees are recognized as products of density-driven flows known as turbidity currents. Compared to the fluvial meandering channels, understanding of the flow and morphodynamics of submarine channels is limited. In this paper, we present experimental results on the morphodynamic and stratigraphic evolution of a submarine channel from sedimentation due to the passage of successive flow events. A pre-formed sinuous channel with multiple bends, a trapezoidal cross section, and an initial thalweg slope of 0.43° was emplaced in a large tank. A total of 29 runs, each lasting an hour, were made by releasing heavier fluids containing salt and silica powder at a constant rate in the tank filled with fresh water. The overbank flow was restricted to curvature-induced flow stripping. The following observations were made from the experimental measurements; (i) asymmetric channel cross sections developed due to higher deposition rates on the outer bank of the channel bends, (ii) an apron or sediment wedge with overlain bedforms appeared near the channel entrance that prograded and aggraded with successive runs, (iii) overbank flow due to flow stripping at bend apices resulted in lobe-shaped deposits, (iv) a higher concentration of solute resulted in flow confinement, and (v) the flow velocity during later runs increased due to channel narrowing and steepening of the gradient.

Ezz, Hesham; Cantelli, Alessandro; Imran, Jasim

2013-05-01

380

Grand Canyon Humpback Chub Population Improving  

USGS Publications Warehouse

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

Andersen, Matthew E.

2007-01-01

381

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

382

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

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

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

383

Metazoan meiofauna in deep-sea canyons and adjacent open slopes: A large-scale comparison with focus on the rare taxa  

NASA Astrophysics Data System (ADS)

Metazoan meiofaunal abundance, total biomass, nematode size and the richness of taxa were investigated along bathymetric gradients (from the shelf break down to ca. 5000-m depth) in six submarine canyons and on five adjacent open slopes of three deep-sea regions. The investigated areas were distributed along >2500 km, on the Portuguese to the Catalan and South Adriatic margins. The Portuguese and Catalan margins displayed the highest abundances, biomass and richness of taxa, while the lowest values were observed in the Central Mediterranean Sea. The comparison between canyons and the nearby open slopes showed the lack of significant differences in terms of meiofaunal abundance and biomass at any sampling depth. In most canyons and on most slopes, meiofaunal variables did not display consistent bathymetric patterns. Conversely, we found that the different topographic features were apparently responsible for significant differences in the abundance and distribution of the rare meiofaunal taxa (i.e. taxa accounting for <1% of total meiofaunal abundance). Several taxa belonging to the temporary meiofauna, such as larvae/juveniles of Priapulida, Holothuroidea, Ascidiacea and Cnidaria, were encountered exclusively on open slopes, while others (including the Tanaidacea and Echinodea larvae) were found exclusively in canyons sediments. Results reported here indicate that, at large spatial scales, differences in deep-sea meiofaunal abundance and biomass are not only controlled by the available food sources, but also by the region or habitat specific topographic features, which apparently play a key role in the distribution of rare benthic taxa.

Bianchelli, S.; Gambi, C.; Zeppilli, D.; Danovaro, R.

2010-03-01

384

Populating a Control Point Database: A cooperative effort between the USGS, Grand Canyon Monitoring and Research Center and the Grand Canyon Youth Organization  

Microsoft Academic Search

The Grand Canyon Monitoring and Research Center measures the effects of Glen Canyon Dam operations on the resources along the Colorado River from Glen Canyon Dam to Lake Mead in support of the Grand Canyon Adaptive Management Program. Control points are integral for geo-referencing the myriad of data collected in the Grand Canyon including aerial photography, topographic and bathymetric data

K. M. Brown; C. Fritzinger; E. Wharton

2004-01-01

385

Financial Analysis of Experimental Releases Conducted at Glen Canyon Dam  

E-print Network

Financial Analysis of Experimental Releases Conducted at Glen Canyon Dam during Water Years 2006 Canyon Dam during Water Years 2006 through 2010 ANL/DIS-11-4 by L.A. Poch,1 T.D. Veselka,1 C.S. Palmer,2 Canyon Dam (GCD) conducted for the U.S. Department of Energy's Western Area Power Administration (Western

Kemner, Ken

386

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

387

CURRICULUM VITAE: THEODORE KENNEDY Grand Canyon Monitoring and Research Center  

E-print Network

CURRICULUM VITAE: THEODORE KENNEDY Grand Canyon Monitoring and Research Center United States/RESEARCH: 2/05 - present. Aquatic Ecologist, Grand Canyon Monitoring and Research Center, USGS, Flagstaff.S. 1/03 - 3/04. Postdoctoral researcher, Grand Canyon Monitoring and Research Center,USGS, Flagstaff

Lovich, Jeffrey E.

388

Wintertime Boundary Layer Structure in the Grand Canyon  

Microsoft Academic Search

Wintertime temperature profiles in the Grand Canyon exhibit a neutral to isothermal stratification during both daytime and nighttime, with only rare instances of actual temperature inversions. The canyon warms during daytime and cools during nighttime more or less uniformly through the canyon's entire depth. This weak stability and temperature structure evolution differ from other Rocky Mountain valleys, which develop strong

C. David Whiteman; Shiyuan Zhong; Xindi Bian

1999-01-01

389

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

Code of Federal Regulations, 2012 CFR

...Representation of submarine cables and pipelines on nautical charts. 209.310 Section...Representation of submarine cables and pipelines on nautical charts. (a) The policy...the locations of submarine cables and pipelines on nautical charts published by the...

2012-07-01

390

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

Code of Federal Regulations, 2010 CFR

...Representation of submarine cables and pipelines on nautical charts. 209.310 Section...Representation of submarine cables and pipelines on nautical charts. (a) The policy...the locations of submarine cables and pipelines on nautical charts published by the...

2010-07-01

391

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

Code of Federal Regulations, 2013 CFR

...Representation of submarine cables and pipelines on nautical charts. 209.310 Section...Representation of submarine cables and pipelines on nautical charts. (a) The policy...the locations of submarine cables and pipelines on nautical charts published by the...

2013-07-01

392

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

Code of Federal Regulations, 2011 CFR

...Representation of submarine cables and pipelines on nautical charts. 209.310 Section...Representation of submarine cables and pipelines on nautical charts. (a) The policy...the locations of submarine cables and pipelines on nautical charts published by the...

2011-07-01

393

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

Code of Federal Regulations, 2014 CFR

...Representation of submarine cables and pipelines on nautical charts. 209.310 Section...Representation of submarine cables and pipelines on nautical charts. (a) The policy...the locations of submarine cables and pipelines on nautical charts published by the...

2014-07-01

394

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

395

50. PIPING FOR SUBMARINE SECTION, Y&D No. 107728 Scale 3/8' ...  

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

50. PIPING FOR SUBMARINE SECTION, Y&D No. 107728 Scale 3/8' = 1'; August 26, 1929 - U.S. Naval Submarine Base, New London Submarine Escape Training Tank, Albacore & Darter Roads, Groton, New London County, CT

396

Determining Spatial and Temporal Inputs of Freshwater, Including Submarine Groundwater Discharge,  

E-print Network

Determining Spatial and Temporal Inputs of Freshwater, Including Submarine Groundwater Discharge. Florida . Submarine groundwater discharge Introduction The timing and sources of freshwater delivery systems while submarine groundwater discharge (SGD) has largely been ignored due, in part, as a result

Miami, University of

397

Supplementary Material A submarine landslide is required to explain the 2011 Tohoku tsunami  

E-print Network

1 Supplementary Material A submarine landslide is required to explain the 2011 Tohoku tsunami]. In contrast, tsunamis generated by a submarine mass failure (SMF; i.e., a submarine landslide), which are more

Kirby, James T.

398

Voluminous submarine lava flows from Hawaiian volcanoes  

SciTech Connect

The GLORIA long-range sonar imaging system has revealed fields of large lava flows in the Hawaiian Trough east and south of Hawaii in water as deep as 5.5 km. Flows in the most extensive field (110 km long) have erupted from the deep submarine segment of Kilauea's east rift zone. Other flows have been erupted from Loihi and Mauna Loa. This discovery confirms a suspicion, long held from subaerial studies, that voluminous submarine flows are erupted from Hawaiian volcanoes, and it supports an inference that summit calderas repeatedly collapse and fill at intervals of centuries to millenia owing to voluminous eruptions. These extensive flows differ greatly in form from pillow lavas found previously along shallower segments of the rift zones; therefore, revision of concepts of volcano stratigraphy and structure may be required.

Holcomb, R.T.; Moore, J.G.; Lipman, P.W.; Belderson, R.H.

1988-05-01

399

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

400

VIRGINIA-Class Submarine: Two for Four in 2012 (B)  

Microsoft Academic Search

The VIRGINIA-class submarine was one of the largest naval-acquisition projects in history, involving the construction of 30 submarines at an acquisition cost of $93 billion. By FY05, the VIRGINIA-class program was in its 10th year. Construction had begun on seven submarines. Unit costs were running 41% over the base-line budget, and production goals were not being met. Ship construction budget

Tom Cross

401

VIRGINIA-Class Submarine: Two for Four in 2012 (A)  

Microsoft Academic Search

The VIRGINIA-class submarine was one of the largest naval-acquisition projects in history, involving the construction of 30 submarines at an acquisition cost of $93 billion. By FY05, the VIRGINIA-class program was in its 10th year. Construction had begun on seven submarines. Unit costs were running 41% over the base-line budget, and production goals were not being met. Ship construction budget

Tom Cross

402

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 dis

403

Geology Fieldnotes: Bryce Canyon National Park, Utah  

NSDL National Science Digital Library

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

Annabelle Foos

404

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.

405

Submarine tower escape decompression sickness risk estimation.  

PubMed

Actions to enhance survival in a distressed submarine (DISSUB) scenario may be guided in part by knowledge of the likely risk of decompression sickness (DCS) should the crew attempt tower escape. A mathematical model for DCS risk estimation has been calibrated against DCS outcome data from 3,738 exposures of either men or goats to raised pressure. Body mass was used to scale DCS risk. The calibration data included more than 1,000 actual or simulated submarine escape exposures and no exposures with substantial staged decompression. Cases of pulmonary barotrauma were removed from the calibration data. The calibrated model was used to estimate the likelihood of DCS occurrence following submarine escape from the United Kingdom Royal Navy tower escape system. Where internal DISSUB pressure remains at - 0.1 MPa, escape from DISSUB depths < 200 meters is estimated to have DCS risk < 6%. Saturation at raised DISSUB pressure markedly increases risk, with > 60% DCS risk predicted for a 200-meter escape from saturation at 0.21 MPa. Using the calibrated model to predict DCS for direct ascent from saturation gives similar risk estimates to other published models. PMID:25109085

Loveman, G A M; Seddon, E M; Thacker, J C; Stansfield, M R; Jurd, K M

2014-01-01

406

Morphostructure and controlling factors on the past and present Gioia-Mesima submarine/channel system (Southern Tyrrhenian Sea, Italy)  

NASA Astrophysics Data System (ADS)

The Gioia-Mesima Canyon-Channel System (GMS) incises the Gioia Basin, a post-Tortonian intra-slope basin extended along the south-eastern Tyrrhenian margin, consisting in a subsiding area controlled by extensional faults. Integration of multibeam, side scan sonar and seismic data with gravity cores has revealed the morpho-stratigraphic and sedimentologic characteristics of the GMS, allowing the identification of the main factors controlling its development and maintenance. The GMS displays a complex morphology consisting in two courses: the Gioia Canyon (GC) and Mesima Canyon-Channel (MC). The courses running parallel, changing from narrow to meandering geometry until they merge in a single lower reach, hanging above the Stromboli Canyon- the main erosive valley of the Gioia Basin. Seismic profiles documented the strong tectonic control on GMS geometry and development. Distensional structures cross-cutting the GMS caused changes in the slope gradient and formed a small intra-slope sub-basin. The progressive infilling of the sub-basin caused changes in GMS base level position, determining a polyphased evolution of the GMS through repeated erosional and depositional events that can be divided in two main stages. The early stage is concurrent with the progressive infilling of the sub-basin. At this time the Gioia and Mesima courses have the same characteristics: narrow erosive canyons along the upper slope and depositional meandering channels in the sub-basin, where the GMS is confined. The GMS erosive-depositional character is revealed by the acoustic facies distribution. The narrow canyons incise a stratified seismic facies (hemipelagic and turbidite deposits) while the meandering channels are confined in a channel-levee seismic facies aggrading over the stratified one. The presence of numerous terraces hanging at several levels above the lower meandering reaches proves the polyphased evolution of the depositional meandering channels. In the later stage, when the confined sub-basin is sufficiently filled, turbiditic flows bypass the Gioia and Mesima Channel-levée system and the GMS base level deepen to the Stromboli Canyon. The base level lowering lead to the single lower reach formation and the rejuvenation of the GMS by upslope incision. At the present time the GC is an erosive shelf-indenting canyon, incising the whole continental slope. It has a narrow and entrenched course strongly deflected by faults and bordered by abandoned terraces in the middle reach. Otherwise, the MS is an abandoned valley hanging on the GC. The present-day different activity of the courses is also documented by the quantitative analysis showing that the GC thalweg longitudinal profile has an irregular convex shape dissected by numerous knickpoints while the MC has an erosive-depositional concave-up longitudinal profile without knickpoints. The positions of the knickpoints upslope tectonic structures and canyon confluences show the retrogressive erosion of the thalweg. The retrogressive development is increased by downslope sediment transport mostly fed by fluvial discharge and retrogressive failures affecting the GC flanks and heads, where tsunamigenic landslides already occurred. The aim of this talk is to summarize the major research results focus on the identification of the controlling factors responsible for the GMS polyphased evolution and present-day contrasting activity of the Gioia and Mesima courses.

Morelli, Eleonora; Martorelli, Eleonora; Latino Chiocci, Francesco

2013-04-01

407

Secondary Circulation in Sinuous Submarine Channels: First Results from the Black Sea  

NASA Astrophysics Data System (ADS)

Sinuous submarine channels are important features on ocean floors, and are key conduits for sediment, carbon and other nutrients into the deep-sea. Their gross planform similarity to river channels has long led to comparison with their subaerial meandering river counterparts. However, they are formed by the action of gravity flows and therefore might be expected to exhibit different processes from the open-channel, single phase flows of river channels. Changes in their morphology and deposits have been observed, however, little is known about the flow processes that occur in these channels. The best available data from modern systems have been limited to single at a point downstream velocity profiles; the best of these being from submarine canyons rather than channels. In order to understand flow dynamics and how they relate to channel processes, sedimentary dynamics and channel evolution, more detailed 2D and 3D flow data is required. Here we report the first such data from a sinuous channel on the Black Sea shelf, and examine the nature of secondary circulation in submarine channels. River channels have long been known to exhibit a three-dimensional helical flow comprising both a dominant downstream component, and a secondary (cross-stream) flow. Such secondary flows are the result of centrifugal acceleration induced by bend curvature, and an inwardly directed radial pressure gradient, which results from a super-elevation of the water surface at the outside of the bend. In river bend apices these secondary flows are directed towards the inner bend at the base of the flow, and towards the outer bank at the top of the flow. Until very recently, it was assumed that submarine channels showed a similar distribution. However, theoretical analysis of the governing equations for river channels, with the incorporation of an appropriate downstream velocity distribution for gravity currents, indicated that submarine channels could display reversed secondary circulation orientation with respect to meandering rivers (Corney et al. 2006, 2008). This theory was backed up by an extensive physical modeling program that also showed reversed secondary circulation in all cases (Keevil et al., 2006, 2007). Other experiments though have shown examples of secondary circulation similar to river channels, and there has been intense debate on the validity of different approaches and datasets. Immediately north of the exit of the Bosphorus Strait, north of Istanbul there is a spectacular sinuous channel network on the Black Sea shelf. This channel network is created by the higher density of seawater of Mediterranean origin as it flows into the much lower salinity Black Sea. The near-constant gravity currents that run through these channels provide the perfect laboratory for studying the detailed fluid dynamics of submarine channel flows. Here we report results from the apex of a major sinuous channel bend that is 20-30 m deep. An acoustic Doppler current profiler (ADCP) towed across the bend recorded a maximum velocity of ~1 m/s. There, the saline underflow is density-stratified, exhibits marked outer-bank super-elevation, and the sense of secondary flow is opposite to that in rivers. Future 3D flow monitoring will use the British autonomous vehicle AutoSub3.

Peakall, J.; Parsons, D. R.; Hiscott, R. N.; Aksu, A. E.; Flood, R. D.; Mouland, D.

2009-05-01

408

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

409

A Submarine Perspective on Hawaiian Volcanoes  

NASA Astrophysics Data System (ADS)

Postwar improvements in navigation, sonar-based mapping, and submarine photography enabled the development of bathymetric maps, which revealed submarine morphologic features that could be dredged or explored and sampled with a new generation of manned and unmanned submersibles. The maps revealed debris fields from giant landslides, the great extent of rift zones radiating from volcanic centers, and two previously unknown submarine volcanoes named Mahukona and Loihi, the youngest Hawaiian volcano. About 70 major landslides cover half the flanks of the Hawaiian Ridge out to Midway Island. Some of the landslides attain lengths of 200 km and have volumes exceeding 5,000 km3. More recent higher resolution bathymetry and sidescan data reveal that many submarine eruptions construct circular, flat-topped, monogenetic cones; that large fields of young strongly alkalic lava flows, such as the North Arch and South Arch lava fields, erupt on the seafloor within several hundred km of the islands; and that alkalic lavas erupt during the shield stage on Kilauea and Mauna Loa. The North Arch flow field covers about 24,000 km2, has an estimated volume between about 1000 and 1250 km3, has flows as long as 108 km, and erupted from over 100 vents. The source and melting mechanisms for their production is still debated. The maps also displayed stair-step terraces, mostly constructed of drowned coral reefs, which form during early rapid subsidence of the volcanoes during periods of oscillating sea level. The combination of scuba and underwater photography facilitated the first motion pictures of the mechanism of formation of pillow lava in shallow water offshore Kilauea. The age progression known from the main islands was extended westward along the Hawaiian Ridge past Midway Island, around a bend in the chain and northward along the Emperor Seamounts. Radiometric dating of dredged samples from these submarine volcanoes show that the magma source that built the chain has been active for over 80 Ma and established the remarkable linearity of the age-progression along the chain. Glass rinds on submarine lava quenched at depth con