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1

Ages of Valles Marineris (Mars) landslides and implications for canyon history  

NASA Astrophysics Data System (ADS)

The chronology of landslides of Valles Marineris, the equatorial trough system of Mars, has been investigated by a crater population study. Valles Marineris landslides have widespread debris aprons which offer a remarkable opportunity to study the crater population with high resolution images from Mars Orbiter Camera (MOC) and from Mars Odyssey Thermal Emission Imaging System (THEMIS). Sixty-six ages were determined within Valles Marineris including 56 landslide ages and 10 ages of the canyon floor. Results reveal that landslides of Valles Marineris system of canyons occurred during a widespread period of time between 3.5 Gy and 50 My. In some locations, the canyon floor has an apparent age of 3.5 Gy suggesting that at least locally within Valles Marineris no major refreshing processes have occurred for 3.5 Gy. The temporal repetitivity of landslides implies that the triggering mechanisms of the landslides are reproducible in time. Landslides have the same features whatever their age. The dynamic of these landslides is probably the same either with intervention of water up to recently (the last 100 My) or without water since 3.5 Gy.

Quantin, C.; Allemand, P.; Mangold, N.; Delacourt, C.

2004-12-01

2

Ages of Valles Marineris (Mars) landslides and implications for canyon history  

Microsoft Academic Search

The chronology of landslides of Valles Marineris, the equatorial trough system of Mars, has been investigated by a crater population study. Valles Marineris landslides have widespread debris aprons which offer a remarkable opportunity to study the crater population with high resolution images from Mars Orbiter Camera (MOC) and from Mars Odyssey Thermal Emission Imaging System (THEMIS). Sixty-six ages were determined

C. Quantin; P. Allemand; N. Mangold; C. Delacourt

2004-01-01

3

Hematite in Valles Marineris, Mars  

Microsoft Academic Search

We investigate the geological context and morphology of hematite deposits in Valles Marineris using data from the Thermal Emission Spectrometer (TES), the Thermal Emission Imaging Spectrometer (THEMIS), Mars Orbiter Camera (MOC), and Mars Orbital Laser Altimeter (MOLA). Observations indicate two classes of deposits within the canyon system. Deposits in Capri Chasma are in-place layered materials at the base of a

A. T. Knudson; P. R. Christensen

2005-01-01

4

Fly in 3D over the Valles Marineris Canyon on Mars (title provided or enhanced by cataloger)  

NSDL National Science Digital Library

This interactive activity lets you explore the Valles Marineris canyon (the size of the US) and a piece of it called the Candor Chasm. Using a 3D model of Mars' surface created using data from orbiting spacecraft, you can examine the surface from a distance, changing lighting to enhance features, and fly over the surface, looking for markers hidden in the terrain. Informative feedback makes the exercise educational as well as fun.

Barstow, Daniel

2003-12-15

5

Mars: Volcanism in the Valles Marineris Overlooked.  

National Technical Information Service (NTIS)

Do volcanic rocks exist in the Valles Marineris. This question is pertinent because the Valles Marineris are gigantic grabens, rivaling rift valleys on earth in size and depth. The Valles Marineris were interpreted as extensional tectonic structures, perh...

B. K. Lucchitta

1988-01-01

6

Hematite in Valles Marineris, Mars  

NASA Astrophysics Data System (ADS)

We investigate the geological context and morphology of hematite deposits in Valles Marineris using data from the Thermal Emission Spectrometer (TES), the Thermal Emission Imaging Spectrometer (THEMIS), Mars Orbiter Camera (MOC), and Mars Orbital Laser Altimeter (MOLA). Observations indicate two classes of deposits within the canyon system. Deposits in Capri Chasma are in-place layered materials at the base of a stack of layers deposited on older chaotic terrain. Deposits in central Valles Marineris (Ophir and Candor Chasmata) are concentrated in topographic lows or benches that are adjacent to bright, layered, sulfate-rich materials. These deposits likely represent hematite-rich lag deposits weathered out of more friable materials, such as adjacent layered deposits. The Capri Chasma hematite deposits are similar in appearance and geological context to the deposit mapped in Aram Chaos. If the central Valles Marineris deposits are lag deposits as described above, they would be comparable to the Meridiani Planum hematite deposits. These results indicate that conditions in each of these two regions of Valles Marineris may have been similar to conditions at Aram Choas and Meridiani Planum at the time of hematite formation. Although two distinct categories of deposit can be established based on morphology and context, all hematite deposits on Mars share compositional commonality. The thermal infrared spectral shape of hematite as derived from TES data is common to all hematite sites so far investigated. Additionally, all sites share similar compositional context. Results from the Observatoire pour la Mineralogie, l'Eau, les Glaces, et l'Activite (OMEGA) team show that sulfate-rich materials occur in, or near, all of the TES identified hematite sites. The hematite is also mixed with basaltic materials as mapped by TES and THEMIS. Researchers have speculated on a variety of mechanisms for the formation of hematite on Mars, but the compositional similarities of all hematite exposures may indicate that all hematite on Mars formed through a similar mechanism. The two distinct categories of deposit may indicate that there were subtle differences in the depositional, post-depositional, or erosional history of these two categories of deposit, but the hematite formation mechanism was most likely common to both categories.

Knudson, A. T.; Christensen, P. R.

2005-12-01

7

Mars: Volcanism in the Valles Marineris overlooked  

NASA Astrophysics Data System (ADS)

Do volcanic rocks exist in the Valles Marineris. This question is pertinent because the Valles Marineris are gigantic grabens, rivaling rift valleys on earth in size and depth. The Valles Marineris were interpreted as extensional tectonic structures, perhaps incipient rifts. On earth, rift valleys commonly contain volcanic deposits. On Mars, deposits inside the Valles Marineris grabens do not have the morphologic signature of such easily identified volcanic features as shield volcanoes or lava flows. Therefore, many researchers have not recognized the deposits inside the Valles Marineris as volcanic. Is Mars, then, different from earth in having formed riftlike grabens unaccompanied by volcanism. Overall, results from the study suggest that volcanism was present in the Valles Marineris; the volcanism was explosive in places; some volcanism was more felsic than that generally assumed elsewhere; and the younger sequence of interior beds was emplaced so late in Martian history that the planet may be considered to be still volcanically active.

Lucchitta, B. K.

8

Investigations of Hematite Deposits in Valles Marineris  

NASA Astrophysics Data System (ADS)

Gray, crystalline hematite deposits have been identified using Mars Global Surveyor (MGS) Thermal Emission Spectrometer (TES) data at three areas of Mars: Meridiani Planum, Aram Chaos, and the Valles Marineris system. Detailed studies of the deposits in Meridiani Planum and Aram Chaos reveal that the hematite occurs in coherent, in-place stratigraphic units. In contrast, the Valles Marineris occurrences are small (5 - 35 km) and scattered throughout the canyon system. The largest hematite deposits are in Ophir and Candor Chasma, where hematite appears to be associated with dark materials near or within the interior layered deposits of the canyon and may represent erosional remnants or in-place units within the layered deposits. A variety of different formational processes have been proposed for these layered deposits, many of which involve liquid water. However, little work has been done to date on the context of the hematite in this locality and the relationship with the layered deposits. This study investigates the details of the hematite occurrences in Valles Marineris, re-mapping hematite occurrence at TES pixel resolution and incorporating multiple datasets to further investigate and interpret the formation, compositional relationships, and history of these deposits. Data from the Mars Odyssey Thermal Emission Imaging System (THEMIS), the MGS Mars Orbiter Camera (MOC), and the MGS Mars Orbiter Laser Altimeter (MOLA) are used along with TES data to map the compositional, thermophysical, and geomorphic context of the hematite deposits throughout the chasma system. Numerous small, isolated occurrences are investigated along with the larger deposits in Ophir and Candor Chasma in order to determine whether the deposits share common origins or represent distinct geologic events.

Knudson, A. T.; Christensen, P. R.

2003-12-01

9

Gray Hematite Distribution within Valles Marineris  

Microsoft Academic Search

Valles Marineris is one of three regions on Mars where TES has identified gray crystalline hematite. In the other two locations, Meridiani Planum and Aram Chaos, a strong correlation between the hematite distribution and geologic units has been found. We have used MOC, THEMIS, and MOLA data to determine if a similar correlation exists for hematite within Valles Marineris. After

C. Weitz; F. S. Anderson

2003-01-01

10

Investigations of Hematite Deposits in Valles Marineris  

Microsoft Academic Search

Gray, crystalline hematite deposits have been identified using Mars Global Surveyor (MGS) Thermal Emission Spectrometer (TES) data at three areas of Mars: Meridiani Planum, Aram Chaos, and the Valles Marineris system. Detailed studies of the deposits in Meridiani Planum and Aram Chaos reveal that the hematite occurs in coherent, in-place stratigraphic units. In contrast, the Valles Marineris occurrences are small

A. T. Knudson; P. R. Christensen

2003-01-01

11

Mars: New evidence for origin of some Valles Marineris layered deposits  

Microsoft Academic Search

The discovery of layered deposits in the walls of a deep trough in Lunae Planum has implications for the origin of similar-appearing deposits in some canyons of Valles Marineris. Although layering is visible in the competent, cliff-forming upper walls of the canyons, the dissimilarity in appearance between canyon walls and soft rounded hills of layered deposits on canyon floors, as

David H. Scott

1993-01-01

12

Gray Hematite Distribution within Valles Marineris  

NASA Astrophysics Data System (ADS)

Valles Marineris is one of three regions on Mars where TES has identified gray crystalline hematite. In the other two locations, Meridiani Planum and Aram Chaos, a strong correlation between the hematite distribution and geologic units has been found. We have used MOC, THEMIS, and MOLA data to determine if a similar correlation exists for hematite within Valles Marineris. After studying the larger patches of hematite within the canyons, we find a correlation between hematite abundance and distinctive geologic units for some patches, but not all. In Ophir and Candor Chasma, the hematite correlates to relatively brighter, dustier units in daytime THEMIS infrared images, but the correlation is moderate and other units with similar infrared properties have no corresponding hematite. Using the narrow angle MOC images, we have determined that the hematite signatures correspond to areas where patches of brighter material are exposed from beneath overlying dark units and dunes. This type of exhumation is similar to the hematite unit at Meridiani Planum. In Eos and Capri Chasma, the hematite appears to cross over geologic units seen in the THEMIS data sets, but no MOC images are available to assess the geology at the higher resolution. The presence of hematite also varies widely with topography, with one patch of hematite occurring across 2 km of relief in central Candor Chasma. In general, hematite occurs more prevalently on the canyon floors adjacent to the interior layered deposits, rather than on the layered deposits themselves. Our current results are based upon the hematite distribution map of Christensen et al. [J. Geophys. Res., 105, 9623-9642, 2000] but we hope to refine these TES compositional maps in order to more precisely correlate hematite to geologic features seen in the MOC and THEMIS data sets.

Weitz, C.; Lane, M.; Anderson, F. S.

2003-12-01

13

Diagenetic haematite and sulfate assemblages in Valles Marineris  

NASA Astrophysics Data System (ADS)

Previous orbital mapping of crystalline gray haematite, ferric oxides, and sulfates has shown an association of this mineralogy with light-toned, layered deposits on the floor of Valles Marineris, in chaos terrains in the canyon's outflow channels, and in Meridiani Planum. The exact nature of the relationship between ferric oxides and sulfates within Valles Marineris is uncertain. The Observatoire pour la Mineralogie, l'Eau, les Glaces et l'Activite (OMEGA) spectrometer initially identified sulfate and ferric oxides in the layered deposits of Valles Marineris. The Thermal Emission Spectrometer (TES) has also mapped coarse (gray) haematite in or at the base of these deposits. We use Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) spectra and Context Camera (CTX) and High Resolution Imaging Science Experiment (HiRISE) imagery from the Mars Reconnaissance Orbiter (MRO) to explore the mineralogy and morphology of the large layered deposit in central Capri Chasma, part of the Valles Marineris canyon system that has large, clear exposures of sulfate and haematite. We find kieserite (MgSO 4·H 2O) and ferric oxide (often crystalline red haematite) in the lower bedrock exposures and a polyhydrated sulfate without ferric oxides in the upper bedrock. This stratigraphy is duplicated in many other basinal chasmata, suggesting a common genesis. We propose the haematite and monohydrated sulfate formed by diagenetic alteration of a sulfate-rich sedimentary deposit, where the upper polyhydrated sulfate-rich, haematite-poor layers either were not buried sufficiently to convert to a monohydrated sulfate or were part of a later depositional phase. Based on the similarities between the Valles Marineris assemblages and the sulfate and haematite-rich deposits of Meridiani Planum, we hypothesize a common evaporite and diagenetic formation process for the Meridiani Planum sediments and the sulfate-bearing basinal Interior Layered Deposits.

Roach, Leah H.; Mustard, John F.; Lane, Melissa D.; Bishop, Janice L.; Murchie, Scott L.

2010-06-01

14

MOC observations of cliff tops and wall rock layering in the Valles Marineris, Mars  

Microsoft Academic Search

New Mars Orbital Camera (MOC) images taken since March of this year with resolutions of up to 1.4 meters per pixel have been obtained of the cliff tops and walls of the Valles Marineris canyons. In many cases, at the cliff edges we observe diverse morphologies not previously seen. We also observe the ubiquitous layering in the canyon walls at

R. A. Beyer; A. S. McEwen

1999-01-01

15

Origin an evolution of the Valles Marineris region of the Mars  

NASA Astrophysics Data System (ADS)

An attempt is made to relate the tectonic interpretation of the wide canyon system of Valles Marineris on Mars to its geomorphic evolution. Tectonic activity due to crustal extension related to the Tharsis-Syria rise (regional doming or lithospheric response to volcanic loading) appears to be the fundamental influence on the canyon formation and evolution. Tectonic activity contributed to the deepening of the canyon system and competed with erosional and depositional processes that caused the canyon to broaden and fill in. Mass wasting, downfaulting, seepage of liquid water and sublimation of ground ice are processes considered.

Masson, Ph.

16

Slope stability analysis of Valles Marineris, Mars  

NASA Astrophysics Data System (ADS)

Valles Marineris (VM) in the equatorial area of Mars exhibits several gravitational failures which resulted in a series of large landslides up to several hundred cubic kilometers in volume. Questions arise as to forces at play and rock strength in the stability of the walls of VM. In this work we address the stability analysis of the walls of VM by considering the strength of the materials of the chasma walls and the causes of landslides. Using finite element calculations and the limit analysis upper bound method, we explore the range of cohesion and friction angle values associated to realistic failure geometries, and compare predictions with the classical Culmann's wedge model. Our analysis is based both on synthetic, simplified slope profiles and also on the real shape of the walls of VM taken from the MOLA topographic data. Validation of the calibrated cohesion and friction angle values is performed by comparing the computed unstable cross sectional areas with the observed pre- and post-failure profiles and estimated failure surface geometry. This offers a link between rock mass properties, slope geometry and volume of the observed failure. Pseudo-static seismic analyses generated another set of dimensionless charts. Our pseudo-static analyses show that low seismicity events induced by meteoroids impacts compatible with the size of craters could be a cause for some of the observed landslides if poor rock properties for VM is assumed.

Vittorio De Blasio, Fabio; Battista Crosta, Giovanni; Castellanza, Riccardo; Utili, Stefano

2013-04-01

17

Formation of the Layered Deposits in the Valles Marineris, Mars.  

National Technical Information Service (NTIS)

Evidence is presented for large standing bodies of water on Mars during past epochs. It is noted that the origin of the horizontally-layered deposits in the Valles Marineris can be best explained by formation in standing bodies of water. These lakes, if t...

S. S. Nedell S. W. Squyres

1987-01-01

18

Extension Across Valles Marineris and the Thaumasia "Rift", Mars  

NASA Astrophysics Data System (ADS)

We calculate extension from topographic profiles. We find the extension across the "Thaumasia Rift" (0.5-4.5 km), a large and complex graben sytem in the Claritas Fossae region, comparable to that across the Tempe Fossae Rift (2.5-3.1 km), but much lower than across Valles Marineris (9-20 km).

Zuschneid, W.; Hauber, E.; Kronberg, P.; Jaumann, R.

2003-03-01

19

Formation of the Layered Deposits in the Valles Marineris, MARS.  

National Technical Information Service (NTIS)

Thick sequences of layered deposits are found in the Valles Marineris, which exhibit fine, nearly horizontal layering, and are present as isolated plateaus of what were once more extensive deposits. It was argued that the morphology of the deposits is mos...

S. S. Nedell S. W. Squyres

1987-01-01

20

New models for the origin of Valles Marineris closed depressions  

SciTech Connect

Current models for the formation of the abundant large closed depressions of Valles Marineris have serious shortcomings. Purely tectonic mechanisms are inconsistent with the morphology of many depressions, and removal of large quantities of ground ice from the canyon walls is inconsistent with the observed strength of the walls. Accordingly, the authors offer some alternatives. One possibility involves decay of ice-rich bodies occupying partially sediment-choked ancient graben that predated the overlying cratered and ridged plains. Other possibilities involve the removal of massive equatorial carbonate deposits storing much of the planet's CO{sub 2} inventory, generated during greenhouse conditions on early Mars. Solution by carbonic acid derived from the atmosphere (analogous to terrestrial karst) requires extensive recycling of the available water supply. Solution by various groundwater acids, possibly derived from the Tharsis magmas, requires less water, especially if only the smaller closed depressions are due to carbonate decay. Alternatively, volume loss due to decarbonation of carbonate during early high heat flow or a later Tharsis-related heat pulse can produce extensive collapse, especially if the carbonates have high silica content.

Spencer, J.R.; Fanale, F.P. (Univ. of Hawaii, Honolulu (USA))

1990-08-30

21

Evidence for precipitation on Mars from dendritic valleys in the Valles Marineris area.  

PubMed

Dendritic valleys on the plateau and canyons of the Valles Marineris region were identified from Thermal Emission Imaging System (THEMIS) images taken by Mars Odyssey. The geomorphic characteristics of these valleys, especially their high degree of branching, favor formation by atmospheric precipitation. The presence of inner channels and the maturity of the branched networks indicate sustained fluid flows over geologically long periods of time. These fluvial landforms occur within the Late Hesperian units (about 2.9 to 3.4 billion years old), when Mars was thought to have been cold. Our results suggest a period of warmer conditions conducive to hydrological activity. PMID:15232103

Mangold, Nicolas; Quantin, Cathy; Ansan, Véronique; Delacourt, Christophe; Allemand, Pascal

2004-07-01

22

Discrete Element Modeling of Landslides in Valles Marineris, Mars  

Microsoft Academic Search

High-resolution MOC, THEMIS, HiRISE, and HRSC image data and geomorphologic characterization based on MOLA-derived topography are being used as input for discrete element modeling to simulate slope failure in Valles Marineris. Two landslides have been selected for detailed analysis. The first landslide, in Coprates Chasma, has a strongly arcuate and recessional 4-km-high main scarp, and a runout length of approximately

K. J. Smart; D. M. Hooper; D. W. Sims

2010-01-01

23

Equatorial glaciations on Mars revealed by gravitational collapse of Valles Marineris wallslopes  

Microsoft Academic Search

Martian global climate models that account for evidence of past glaciations reported in tropical to mid-latitude regions of Mars predict accumulation of water ice in Valles Marineris during past periods of high obliquity. Observational evidence for such glaciations is given here. Topographic basement ridges of tectonic origin are common in Valles Marineris, and display sackung features, an assemblage of tectonic

Daniel Mège; Olivier Bourgeois

2011-01-01

24

Origin and evolution of the layered deposits in the Valles Marineris, Mars  

SciTech Connect

Four hypotheses are discussed concerning the origin of the layered deposits in the Martian Valles Marineris, whose individual thicknesses range from about 70 to 300 m. The hypothesized processes are: (1) aeolian deposition; (2) deposition of remnants of the material constituting the canyon walls; (3) deposition of volcanic eruptions; and (4) deposition in standing bodies of water. The last process is chosen as most consistent with the rhythm and lateral continuity of the layers, as well as their great thickness and stratigraphic relationship with other units in the canyons. Attention is given to ways in which the sediments could have entered an ice-covered lake; several geologically feasible mechanisms are identified. 46 references.

Nedell, S.S.; Squyres, S.W.; Andersen, D.W.

1987-06-01

25

Are there carbonate deposits in the Valles Marineris, Mars?  

NASA Astrophysics Data System (ADS)

The precipitation of 30 mbar of Martian atmosphere CO2 as carbonates in lakes is suggested to be the source of thick sequences of layered deposits found in the Valles Marineris. Support is adduced for this scenario from processes occurring in the perennially frozen dry valley lakes of Antarctica, where the lake water is supersaturated with atmospheric gases. Atmospheric CO2 would have accumulated in such Martian lakes as temperatures fell, and the presence of an insulating ice cover would have allowed liquid water to exist.

McKay, C. P.; Nedell, S. S.

1988-01-01

26

Optical depth and its scale-height in Valles Marineris from HRSC stereo images  

NASA Astrophysics Data System (ADS)

We measured the optical depth of the Martian atmosphere as a function of altitude above two opposing scree walls of the Valles Marineris, from stereo images that were taken with the High Resolution Stereo Camera (HRSC) of Mars Express on June 3, 2004, during orbit 471. The optical depths were measured from contrast differences between the stereo images with the so called "stereo method". For 7 regions in the northern wall of the Valles, we estimated the optical depth and found values between 1.0 and 1.6. These regions span more than 6 km in altitude and the results show a clear relation with altitude. A fit on these results yielded a scale-height for the optical depth of 14.0 km + 1.3/-1.1 km. The expected local pressure-scale height is smaller: 11.5-12.0 km. The difference is most likely explained by small (around 1.5%) offset errors in the intensity calibration of HRSC images. We also selected 9 regions in the opposing southern wall and from these we measured values of optical depth in the range 1.3-1.5. Our result suggests the presence of clouds above this part of the Valles because the optical depth appears almost independent of the surface altitude. Possibly these are banner clouds, forming at the edge of the canyon, that contain dust that is blown over the canyon by winds from the high plains to the South.

Hoekzema, N. M.; Garcia-Comas, M.; Stenzel, O. J.; Grieger, B.; Markiewicz, W. J.; Gwinner, K.; Keller, H. U.

2010-06-01

27

Dark materials in Valles Marineris: Indications of the style of volcanism and magmatism on Mars  

SciTech Connect

Rifting on the equatorial canyon system of Valles Marineris provides a unique view of the interior of the Martian crust to depths reaching 7 km, exposing several in situ bedrock units which testify to past volcanic and magmatic processes on Mars. A thick, regionally extensive deposit observed in Coprates and Juventae chasmata is interpreted on the basis of spectral reflectance, erosional morphology, and tendency for eolian mobilization to be composed of mafic glass, possibly an ancient Martian analogue of the lunar terra mantling deposits. Spectral mapping suggests that the dark floor-covering materials in the lower canyons are derived from this unit. A series of cliffs in the Ophir Chasma wall rock is interpreted to be exposures of resistant bedrock; the spectral signature of this massive and uniform unit most closely resembles that of terrestrial mafic rocks altered to or coated by crystalline hematite. Application of computer mapping techniques to probable young volcanic materials in the central troughs yields an inferred distribution of volcanic activity consistent with the interpretation of extrusion along faults near the margins of the canyon floors. This result supports the hypothesis that the valles originated through tectonic extension.

Geissler, P.E.; Singer, R.B. (Univ. of Arizona, Tucson (USA)); Lucchitta, B.K. (Geological Survey, Flagstaff, AZ (USA))

1990-08-30

28

The Geologic Context of Water-altered Minerals in Valles Marineris  

NASA Astrophysics Data System (ADS)

We investigated hematite and sulfate (polyhydrated sulfates and kieserite) sites throughout the Valles Marineris complex, with a variety of remote-sensing tools, in order to better understand the correlation between different mineral types and their likel

Chojnacki, M.; Hynek, B. M.

2007-03-01

29

Valles Marineris, Mars: Are Pit Chains Formed by Erosion and Troughs by Tectonism.  

National Technical Information Service (NTIS)

The origin of the Valles Marineris remains controversial. Erosional, tectonic, and hybrid processes have been proposed. To clarify these contradictions, the widths and depths of pit chains and troughs were compared and it was found that the features do no...

B. K. Lucchitta R. A. Balser L. M. Bertolini

1991-01-01

30

Stratigraphic architectures spotted in southern Melas Chasma, Valles Marineris, Mars  

NASA Astrophysics Data System (ADS)

The distribution in space and time of liquid water on Mars is relevant to astrobiology and astroclimatology. To date, most orbital observations that attest to past fluvial and lacustrine activity on Mars have been dedicated to surficial landforms (i.e., drainage networks and depositional fans). Here we report an unprecedented identification of typical stratigraphic architectures made in Mars Global Surveyor Mars Orbiter Camera images of layered material in southern Melas Chasma. A particular set of strata is arranged in three depositional sequences bounded by stratigraphic unconformities. The sequences show spectacular steeply inclined clinoforms, and a broad channel-like depression. There are the same complex stratal patterns in Valles Marineris on Mars as there are in terrestrial deposits. Insights into these three-dimensional deposit geometries are used to tentatively isolate specific depositional processes and point to ancient subaqueous settings. Findings in southern Melas indicate a very attractive spot to which the search for ancient habitable environments on Mars could be directed.

Dromart, Gilles; Quantin, Cathy; Broucke, Olivier

2007-04-01

31

Hematite in Valles Marineris: Context, Composition, Distribution, Morphology, Physical Properties, and Comparison to Other Mars Hematite Deposits  

NASA Astrophysics Data System (ADS)

Gray, crystalline hematite deposits have been identified by data from MGS TES at three areas on Mars: Meridiani Planum, Aram Chaos, and Valles Marineris. Remote sensing studies of the deposits at Meridiani Planum and Aram Chaos indicate that hematite occurs in relatively large, coherent, in-place stratigraphic units. In situ studies at the Meridiani Planum site by the MER Opportunity have revealed that the hematite is likely carried in spheroidal concretions that form lag deposits as they weather out of in-situ sedimentary layered deposits. The hematite occurrences in Valles Marineris are small, 5 - 35 km in diameter, and are discontinuous throughout the canyon system. In this study THEMIS, MOC, MOLA and TES data are used to investigate the geomorphology, composition, and thermophysical characteristics of hematite bearing deposits throughout the canyon system and compare them to the other hematite deposits on Mars. Hematite bearing deposits in Valles Marineris span an total elevation range of 5600m. Preliminary evaluation indicates no clear correlation of with latitude or longitude. In Ophir and Candor Chasmata, hematite is associated with relatively dark materials near or within interior layered deposits and may represent in-place units or erosional remnants. Deconvolution of TES spectra from Candor Chasma show hematite abundances from 5 to 12%. Associated materials exhibit compositions similar to TES Surface Type II, which has been described as a basaltic andesite or weathered basalt. In Capri Chasma hematite signatures generally correlate with layered units, which lie at similar elevations, and are within 1km of the mean. Dunes overlying and obscuring layered deposits do not contain hematite. Benches and breaks in slope near the boundaries of many layered deposits provide further evidence that the layers may represent in-place, stratigraphic units. Hematite in Capri Chasma may have formed in a single event, which involved deposition or reworking in standing water.

Knudson, A. T.; Christensen, P. R.

2004-12-01

32

Light-toned deposits in Valles Marineris, on crater bulges, and in chaos: do they have a common origin as spring deposits?  

Microsoft Academic Search

Layered, massive or mound-shaped light-toned deposits are present at several locations on Mars. They include crater bulges (e.g. Gale), Interior Layered Deposits in Valles Marineris canyon system (e.g. Candor Chasma), bright deposits in chaotic terrains (e.g. Aram Chaos). Despite the differences among these various kinds of deposits and morphologies, they all share some features, such as layering, and a similar

A. Rossi; G. Neukum; M. Pondrelli; T. Zegers; G. Ori; E. Hauber; P. Mason; A. Chicarro

2006-01-01

33

Analysis of Fault Lengths Across Valles Marineris, Mars  

NASA Astrophysics Data System (ADS)

Summary. As part of a larger project to determine the history of stress and strain across Valles Marineris, Mars, graben lengths located within the Valley are measured using a two-dimensional window-sampling method to investigate depth of faulting and accuracy of measurement. The resulting degree of uncertainty in measuring lengths (+19 km - 80% accuracy) is independent of the resolution at which the faults are measured, so data sets and resultant statistical analysis from different scales or map areas can be compared. The cumulative length frequency plots show that the geometry of Valley faults display no evidence of a frictional stability transition at depth in the lithosphere if mechanical interaction between individual faults (an unphysical situation) is not considered. If strongly interacting faults are linked and the composite lengths used to re-create the cumulative lengths plots, a significant change in slope is apparent suggesting the existence of a transition at about 35-65 km below the surface (assuming faults are dipping from 50deg to 70deg This suggests the thermal gradient to the associated 300-400degC isotherm is 53C/km to 12degC/km.

Fori, A. N.; Schultz, R. A.

1996-03-01

34

Pristine Noachian crust and key geologic transitions in the lower walls of Valles Marineris: Insights into early igneous processes on Mars  

NASA Astrophysics Data System (ADS)

Valles Marineris is a unique vertical section through the uppermost kilometers of the martian crust. Its location, east of the Tharsis bulge, and its water-related history, fuel a great diversity of rock types in this area (Carr, M.H., Head, J.W. [2010]. Earth Planet. Sci. Lett. 294, 185-203). HiRISE and CRISM data available over the walls of the canyon were analyzed to infer the importance of magmatic and sedimentary processes through time. This contribution provides a complete morphologic and mineralogic characterization of the cross-section of rocks exposed in the canyon walls. Low-calcium pyroxene and olivine are detected in the lower portion of the walls, in association with morphologically distinct outcrops, leading to the idea that pristine Noachian crust might be exposed. Phyllosilicates are also present within the walls, but they appear to correspond to an alteration product. No proper sedimentary layers were observed within the walls of Valles Marineris at the resolution available today. All these detections are limited to the eastern portion of Valles Marineris, especially Juventae, Coprates, Capri, and Ganges chasmata. Preserved Noachian crustal material is rare on the martian surface and is rarely exposed in its pristine geologic context. Such detections lend precious information about early igneous processes. This survey also supports observations from the nearby impact crater central peaks (Quantin, C., Flahaut, J., Allemand, P. [2009]. Lunar Planet. Sci. 10; Quantin, C., Flahaut, J., Clenet, H., Allemand, P., Thomas, P. [2011]. Icarus, submitted for publication) and suggests that the western part of Valles Marineris may be cut into another material, consistent with lavas or volcanic sediments.

Flahaut, Jessica; Quantin, Cathy; Clenet, Harold; Allemand, Pascal; Mustard, John F.; Thomas, Pierre

2012-09-01

35

Valles Marineris, Mars: Are pit chains formed by erosion and troughs by tectonism?  

Microsoft Academic Search

The origin of the Valles Marineris remains controversial. Erosional, tectonic, and hybrid processes have been proposed. To clarify these contradictions, the widths and depths of pit chains and troughs were compared and it was found that the features do not form a continuum. Rather, results are consistent with the hypothesis that pit chains formed by surficial collapse and troughs by

Baerbel K. Lucchitta; R. A. Balser; L. M. Bertolini

1991-01-01

36

Multiple-process origin of Valles Marineris basins and troughs, Mars  

Microsoft Academic Search

An improved sequence of formation for Valles Marineris depressions is proposed. It involves three key stages; (a) dike emplacement radial to Syria Planum during Late Noachian to Early Hesperian time; (b) localized subsidence of crustal rocks during post-Early Hesperian time, forming ancestral basins such as Hebes Chasma; and (c) regional normal faulting that overprints the ancestral basins and forms the

Richard A. Schultz

1998-01-01

37

Structural development of Coprates Chasma and western Ophir Planum, Valles Marineris Rift, Mars  

Microsoft Academic Search

A portion of Valles Marineris was mapped in detail in order to clarify the dominant processes responsible for the formation of Coprates Chasma. New crater counts indicate that the caprock on western Ophir Planum plateau has a Late Hesperian crater age, whereas trough floor preserved in western Coprates Chasma has an Early to Late Hesperian crater age. Caprock on western

Richard A. Schultz

1991-01-01

38

Landslides in Valles Marineris (Mars): A possible role of basal lubrication by sub-surface ice  

Microsoft Academic Search

There is much interest on the occurrence of water and ice in the past history of Mars. Because landslides on Mars are much better conserved than their terrestrial counterparts, a physical examination and morphological analysis can reveal significant details on the depositional environment at the instant of failure. A study of the landslides in Valles Marineris based on their physical

Fabio Vittorio de Blasio

2011-01-01

39

Topography of Valles Marineris: Implications for erosional and structural history  

NASA Astrophysics Data System (ADS)

Compilation of a simplified geologic/geomorphic map onto digital terrain models of the Valles Marineris permitted an evaluation of elevations in the vicinity of the troughs and the calculation of depth of troughs below surrounding plateaus, thickness of deposits inside the troughs, volumes of void spaces above geologic/geomorphic units, and volumes of deposits. The central troughs north Ophir, north and central Candor, and north Melas Chasmata lie as much as 11 km below the adjacent plateaus. In Ophir and Candor chasmata, interior layered deposits reach 8 km in elevation. If the deposits are lacustrine and if all troughs were interconnected, lake waters standing 8 km high would have spilled out of Coprates Chasma onto the surrounding plateaus having surface elevations of only 4-5 km. On the other hand, the troughs may not have been interconnected at the time of interior-deposit emplacement; they may have formed isolated ancestral basins. The existence of such basins is supported by independent structural and stratigraphic evidence. The ancestral basins may have eventually merged, perhaps through renewed faulting, to form northern subsidiary troughs in Ophir and Candor Chasmata and the Coprates/north Melas/Ius graben system. The peripheral troughs are only 2-5 km deep, shallower than the central troughs. Chaotic terrain is seen in the peripheral troughs near a common contour level of about 4 km on the adjacent plateaus, which supports the idea of release of water under artesian pressure from confined aquifers. The layered deposits in the peripheral troughs may have formed in isolated depressions that harbored lakes and predated the formation of the deep outflow channels. (If these layered deposits are of volcanic origin, they may have been emplaced beneath ice in the manner of table mountains.) Areal and volumetric computations show that erosion widened the troughs by about one-third and that deposits occupy one-sixth of the interior space. Even though the volume eroded is larger than the volume deposited, topographic and geologic considerations imply that material eroded from trough walls was probably part of the interior layered deposits but not their sole source. Additional material may have come from subterranean piping, from reworking of local disintegration products on the floors, such as chaotic materials, or from eolian influx. But overall it is likely that the additional material is volcanic and that it forms mostly the upper, more diversely bedded layers of the interior deposits.

Lucchitta, B. K.; Isbell, N. K.; Howington-Kraus, A.

1994-02-01

40

Mars Surveyor Landing Sites in Valles Marineris: Highland Rocks from the Basement Using the Marie-Curie Lander  

NASA Astrophysics Data System (ADS)

Two potential landing sites in the central Valles Marineris for the 2001 lander-rover mission emphasize geologic context and trough location for examining Noachian rocks. Mission results would favorably impact local, regional, and global issues.

Schultz, R. A.

1999-03-01

41

Spectral Evidence for Aqueous Alteration of the Plains Surrounding Valles Marineris, Mars  

NASA Astrophysics Data System (ADS)

Data from the high-resolution CRISM visible-near infrared spectrometer onboard the MRO spacecraft reveal the presence of hydrous phases in the plains surrounding the Valles Marineris canyon system. These phases can be classified as either, phyllosilicates or, more generally, hydrated silicates. CRISM spectra of the former are consistent with Al and Fe/Mg-bearing smectites, whereas those of the latter may represent the presence of amorphous silica, hydrated glass (impact or volcanic), chalcedony, opal, or other hydrated Si-rich phases. The phyllosilicates occur in rough textured, light-toned, Noachian age outcrops exposed on the plains along the western portions of the canyon system, including the regions south of Eos and Coprates Chasma and in the walls of Ganges and Coprates Chasma. The presence of layering or total thickness of these deposits is currently unclear, but they are commonly covered by a thin, darker unit and it is likely that their lateral extent is greater than the size of the individual exposures. The spectra for these exposures exhibit H2O features near 1.4 and 1.9 um and Al-OH or Fe/Mg-OH combination bands near 2.2 or 2.3 um, respectively. The spectra are most consistent with smectites such as montmorillonite, nontronite, and/or saponite. In contrast, the hydrated silicates are found primarily in layered materials that exhibit parallel beds that vary in thickness and albedo in the Hesperian aged plains south of Melas and Ius Chasma and west of Juventae Chasma. The spectra and the smooth morphology and light-toned color of these units as observed in accompanying HiRISE and CTX images are inconsistent with lava flows and imply a pyroclastic, aeolian, or fluvial/lacustrine origin instead. Cross-bedding or other sedimentary structures indicative of aeolian or fluvial processes have not been observed to date, but this may be limited by the spatial resolution of the images or inadequate sampling of these units. Spectra of these materials exhibit H2O absorptions at 1.4, 1.9, and 3 um and an OH feature near 2.21 um, though sometimes this feature appears as a weaker band near 2.23 um. The OH feature is broader and sometimes more rounded than similarly positioned bands in Al-bearing phyllosilicates such as montmorillonite. The occurrences of these phases in the plains around V. Marineris do not appear to be associated with or directly adjacent to exposures of phyllosilicates or sulfates. The presence of phyllosilicates in the Noachian crust along V. Marineris, combined with observations of similar materials exposed throughout the ancient cratered highlands, suggests widespread aqueous alteration of the primary crust during the Noachian and is consistent with the model of Bibring et al. (2006). In contrast, the hydrated silicates in the Hesperian plains do not follow the convention of this model. Their composition may represent variations in parent lithology (e.g. volcanic ash instead of basalt), fluid chemistry, climatic changes, or a combination of these factors. Understanding the origin, age, relationship to other hydrous phases, and widespread of these phases may provide a better understanding of the transition from a phyllosilicate to sulfate dominated era on Mars.

Milliken, R. E.; Swayze, G.; Murchie, S.; Bishop, J.; Clark, R.; Ehlmann, B.; Grtozinger, J.; Mustard, J.; Weitz, C.

2007-12-01

42

Layering in the wall rock of Valles Marineris: intrusive and extrusive magmatism  

NASA Astrophysics Data System (ADS)

High-resolution images of the walls exposed in Valles Marineris reveal variations in appearance and degree of layering indicating various lithologies comprise the Tharsis plateau. The layered wall rock has been proposed to result from effusive flood basalt volcanism or interbedded sediments and volcanics. We present observations of unlayered rock that indicate layering extends to a greater depth in the western half of Valles Marineris and is confined to the Tharsis plateau, a region of thickened, uplifted crust resulting from prolonged intrusive activity. Consistent with this view, we propose that the observed layering may be a manifestation of intrusive rocks resulting from crystal fractionation of intruded basaltic magmas. Terrestrial layered plutons provide analogs for comparison such as those of the North Atlantic Igneous Province (NAIP) a large igneous province associated with crustal rifting and exposures of thick sequences of layered flood basalts and intruded layered cumulates.

Williams, Jean-Pierre; Paige, David A.; Manning, Craig E.

2003-06-01

43

Geological context of water-altered minerals in Valles Marineris, Mars  

Microsoft Academic Search

Greater than 15,000 km2 of the layered deposits within Valles Marineris are associated with water-altered minerals, yet their origin and history of alteration remain a mystery. There are numerous competing hypotheses for the formation of the interior layered deposits including aeolian, lacustrine, and volcanic. Recent orbiter spectroscopic data have indicated that water has played a role in their geological history.

Matthew Chojnacki; Brian M. Hynek

2008-01-01

44

New Evidence for the Origin of Layered Deposits in Valles Marineris  

Microsoft Academic Search

Results from CRISM, HiRISE, and CTX on MRO provide new insights into the origin of interior layered deposits (ILDs) in Valles Marineris. A well-exposed, thick sequence in western Candor Chasma has spectral properties consistent with basaltic sand mixed with nanophase iron oxide-rich dust, with the addition of sulfates and crystalline ferric oxides. Most of the deposit is dominated spectrally by

S. Murchie; F. Seelos; L. Roach; J. Mustard; R. Milliken; R. Arvidson; S. Wiseman; K. Lichtenberg; J. Andrews-Hanna; J. Bibring; J. Bishop; M. Parente; R. Morris

2008-01-01

45

Strike-slip faulting of ridged plains near Valles Marineris, Mars  

NASA Astrophysics Data System (ADS)

This paper identifies and documents several well-preserved examples of Martian strike-slip faults and examines their relationships to wrinkle-ridges. The strike-slip faulting predates or overlaps periods of wrinkle-ridge growth southeast of Valles Marineris, and some wrinkle ridges may have nucleated and grown as a result of strike-slip displacements along the echelon fault arrays. Lateral displacements of several km inferred along these arrays may be related to tectonism in Tharsis.

Schultz, R. A.

1989-10-01

46

Volcanism and FluvioGlacial Processes on the Interior Layered Deposits of Valles Marineris, Mars?  

Microsoft Academic Search

The Interior Layered Deposits (ILDs) in Valles Marineris have been suggested to be possible sub-ice volcanoes. Recent images also show evidence of possible fluvio-glacial processes on the ILDs and hence volcano\\/ice\\/water interaction. For example, Mars Express Mission anaglyph from Orbit 334 of central Ophir and Candor Chasmata, THEMIS image V10551002, and MOC images E1700142 and E190020 show 2 ILD mounds

M. G. Chapman

2005-01-01

47

Geologic Analysis of a Possible Oasis and Environs in the Valles Marineris, Mars  

NASA Astrophysics Data System (ADS)

We used Mars Global Surveyor data from TES, MOC, and MOLA to examine the geologic history of a region of interior layered deposits on the floor of western Candor Chasma in the Valles Marineris, Mars. This site was characterized by Geissler et al. (1993, Icarus 106) as having an unusual reddish color in multispectral images from Viking and Phobos missions. The red color was associated with two 20-km-long depressions and was thought to indicate the presence of crystalline ferric oxides (possibly hematite) in the layered deposits. Assuming that water was required to form the iron oxides via aqueous or hydrothermal alteration, these depressions may mark the site of a local oasis involving ponding or groundwater seepage in the canyon. Thermal inertia and dust index images from TES data of west Candor Chasma indicate that mantling and obscuration of local outcrops is not significant in the region of the possible oasis. To characterize the mineralogy of this area, we use multiple-endmember spectral mixture analysis (MESMA) to deconvolve TES emissivity data relative to laboratory spectra of minerals. This method identifies the minimum number of components (4 to 5) required to model the spectrum of each pixel in the spectral ranges of 307-507 cm-1 and 825-1301 cm-1 (66 TES channels) through iterative comparisons to a 33-component mineral spectral library. This library, adapted from that of ASU, includes pyroxenes, plagioclase feldspars, clays, micas, amphiboles, sulfates, carbonates, olivines, K-spar, gray hematite, and volcanic glass, plus 5 atmospheric endmembers and a blackbody. Although nanophase red hematite is undistinguished at TES wavelengths, mineral abundance maps indicate the presence of other Fe-rich minerals (such as nontronite and Fe-smectite) at this site. Gray hematite, hi-Ca clinopyroxene, Fe-rich olivine, and hi-Ca plagioclase minerals are also observed within layered deposits in the canyon walls and interior, as well as in dark materials at the base of canyon walls. These results suggest that we are mapping sites of alteration and volcanism in west Candor Chasma with the TES data. We are currently performing photoclinometric modeling of coregistered MOC (6 m/pixel) and MOLA (500 m/pixel) data via the method of Soderblom et al. (2002, LPS\\ #1254) to evaluate the orientation and possible origin of this layered deposit.

Gaddis, L. R.; Staid, M. I.; Titus, T. N.

2002-12-01

48

Landslides in Valles Marineris (Mars): A possible role of basal lubrication by sub-surface ice  

NASA Astrophysics Data System (ADS)

There is much interest on the occurrence of water and ice in the past history of Mars. Because landslides on Mars are much better conserved than their terrestrial counterparts, a physical examination and morphological analysis can reveal significant details on the depositional environment at the instant of failure. A study of the landslides in Valles Marineris based on their physical aspect is presented and the velocity of the landslides is calculated with a stretching block model. The results show that the landslides were subject to strong basal lubrication that made them travel at high speed and to long distances. We use physical analysis to explore the four alternative possibilities that the natural lubricant of the landslides in Valles Marineris was either ice, deep water, a shallow carpet of water, or evaporites. Examination of the furrows present on the surface of the landslide deposits shows that either sub-surface ice or evaporites were likely present on the floor of Valles Marineris during the mass failures.

De Blasio, Fabio Vittorio

2011-10-01

49

Slope stability analysis for Valles Marineris, Mars: a numerical analysis of controlling conditions and failure types  

NASA Astrophysics Data System (ADS)

Valles Marineris (VM hereafter) in the equatorial area of Mars exhibits several gravitative failures often involving the whole 6-8 km thickness of the valley walls. The failures have resulted in a series of long-runout landslides up to several hundred cubic kilometres in volume (Quantin et al., 2004), and the formation of sub-circular alcoves perched on the top. Several questions arise as to forces at play in the stability of the walls of VM, the geometrical shape of the alcoves and the shape and long-runout of the landslides (see for example Lucas et al., 2011). In this work, we concentrate on the stability analysis of the walls of VM with two precise questions in mind starting from past studies (Bigot-Cormier and Montgomery, 2006; Neuffer and Schultz, 2006, Schultz, 2002). The first concerns the properties of the materials that give origin to instability. We performed several finite element and discrete element calculations tailored to slope stability analysis based on the genuine shape of the walls of VM taken from the MOLA topographic data. We considered stratified and differently altered/degraded materials to define the range of physical mechanical properties required for failure to occur and to explain the discrete distribution of failures along the VM valley flanks. A second question addressed in this work is the geometrical shape of the sub-circular alcoves. Normally, these shapes are commonplace for slopes made of uniform and isotropic properties, and are also observed in subaqueous environment. We performed calculations taking into consideration the progressive failure in the slope showing the final results in terms of surface failure geometry. Bigot-Cormier, F., Montgomery, D.R. (2007) Valles Marineris landslides: Evidence for a strength limit to Martian relief? Earth and Planetary Science Letters, 260, 1-2, 15, 179-186 Lucas, A., Mangeney, A., Mège, D., and Bouchut, F., 2011. Influence of the scar geometry on landslide dynamics and deposits: Application to Martian landslides, J. Geophys. Res. - Planets, 116, E10001, DOI: 10.1144/1470-9236/05-042 Quantin, C., Allemand, P., Delacourt, C. (2004) Morphology and geometry of Valles Marineris landslides. Planetary and Space Science, 52, 11, 1011-1022 Neuffer, D.P., R.A. Schultz (2006) Mechanisms of slope failure in Valles Marineris, Mars. Quarterly Journal of Engineering Geology and Hydrogeology, 39,.3, 227-240 Schultz, R.A. (2002) Stability of rock slopes in Valles Marineris, Mars. Geophysical Research Letters, 29, 1932, doi:10.1029/2002GL015728

Crosta, G.; Castellanza, R.; De Blasio, F.; Utili, S.

2012-04-01

50

Thin-skinned deformation of sedimentary rocks in Valles Marineris, Mars  

USGS Publications Warehouse

Deformation of sedimentary rocks is widespread within Valles Marineris, characterized by both plastic and brittle deformation identified in Candor, Melas, and Ius Chasmata. We identified four deformation styles using HiRISE and CTX images: kilometer-scale convolute folds, detached slabs, folded strata, and pull-apart structures. Convolute folds are detached rounded slabs of material with alternating dark- and light-toned strata and a fold wavelength of about 1 km. The detached slabs are isolated rounded blocks of material, but they exhibit only highly localized evidence of stratification. Folded strata are composed of continuously folded layers that are not detached. Pull-apart structures are composed of stratified rock that has broken off into small irregularly shaped pieces showing evidence of brittle deformation. Some areas exhibit multiple styles of deformation and grade from one type of deformation into another. The deformed rocks are observed over thousands of kilometers, are limited to discrete stratigraphic intervals, and occur over a wide range in elevations. All deformation styles appear to be of likely thin-skinned origin. CRISM reflectance spectra show that some of the deformed sediments contain a component of monohydrated and polyhydrated sulfates. Several mechanisms could be responsible for the deformation of sedimentary rocks in Valles Marineris, such as subaerial or subaqueous gravitational slumping or sliding and soft sediment deformation, where the latter could include impact-induced or seismically induced liquefaction. These mechanisms are evaluated based on their expected pattern, scale, and areal extent of deformation. Deformation produced from slow subaerial or subaqueous landsliding and liquefaction is consistent with the deformation observed in Valles Marineris.

Metz, Joannah; Grotzinger, John; Okubo, Chris; Milliken, Ralph

2010-01-01

51

Hematite in Valles Marineris: Context, Composition, Distribution, Morphology, Physical Properties, and Comparison to Other Mars Hematite Deposits  

Microsoft Academic Search

Gray, crystalline hematite deposits have been identified by data from MGS TES at three areas on Mars: Meridiani Planum, Aram Chaos, and Valles Marineris. Remote sensing studies of the deposits at Meridiani Planum and Aram Chaos indicate that hematite occurs in relatively large, coherent, in-place stratigraphic units. In situ studies at the Meridiani Planum site by the MER Opportunity have

A. T. Knudson; P. R. Christensen

2004-01-01

52

New Evidence for the Origin of Layered Deposits in Valles Marineris  

NASA Astrophysics Data System (ADS)

Results from CRISM, HiRISE, and CTX on MRO provide new insights into the origin of interior layered deposits (ILDs) in Valles Marineris. A well-exposed, thick sequence in western Candor Chasma has spectral properties consistent with basaltic sand mixed with nanophase iron oxide-rich dust, with the addition of sulfates and crystalline ferric oxides. Most of the deposit is dominated spectrally by the dust component. Monohydrated and polyhydrated sulfates are concentrated in separate, interbedded layers, which in some cases are traceable over tens of kilometers. Monhydrated sulfates dominate the lower part of the deposits whereas polyhydrated sulfates are more common in upper strata. The deposits are partially mantled by low- albedo eolian ripples that contain pyroxenes similar in composition to what is found on the surrounding plateau, plus sulfates predominantly in monohydrated form. The dark ripples originate from discrete, friable layers. Similar dark, erodible layers elsewhere on Mars have been interpreted as buried eolian sand. Crystalline ferric oxides are concentrated in the sulfate-rich layers, and mass wasting has accumulated them at the base of steep slopes to form the deposits of gray hematite detected by TES. The persistence of monohydrated sulfates in debris shows that alteration of monohydrated to polyhydrated sulfates, proposed as an important weathering process, takes long compared to formation of the thin layer that dominates reflectance properties. The observed stratification of sulfate compositions implies differences in the abundance of liquid water or brine chemistry during deposition or early chemical modification of sediments. Inferred mineralogy and compositional stratification are similar to what is observed in sulfate-rich sediments in the Meridiani and Aram Chaos regions. The Meridiani deposits were proposed to accumulate where evaporites formed in areas of groundwater discharge and cemented eolian sediments, in which coarse- grained hematite formed by diagenetic alteration. Modeling of the history of groundwater discharge in Valles Marineris shows that thick evaporite sequences are also expected within the chasmata, and could have similarly trapped eolian sediments. Areas with predicted thick accumulations enclose the major eroded remnants of the ILDs. Formation of the ILDs by lithification of eolian sediment by evaporites in areas of groundwater discharge links the spectrally and morphologically similar, sulfate- and ferric-oxide bearing deposits in Valles Marineris, Aram Chaos, and Meridiani to a common regional process.

Murchie, S.; Seelos, F.; Roach, L.; Mustard, J.; Milliken, R.; Arvidson, R.; Wiseman, S.; Lichtenberg, K.; Andrews-Hanna, J.; Bibring, J.; Bishop, J.; Parente, M.; Morris, R.

2008-12-01

53

Stratigraphy and erosional landforms of layered deposits in Valles Marineris, Mars  

NASA Astrophysics Data System (ADS)

Satellite imagery is used to identify stratigraphy and erosional landforms of 13 layered deposits in the Valles Marineris region of Mars (occurring, specifically, in Gangis, Juventae, Hebes, Ophir-Candor, Melas, and Capri-Eos Chasmata), based on albedo and erosional styles. Results of stratigraphic correlations show that the stratigraphy of layered deposits in the Hebes, Juventae, and Gangis Chasmata are not well correlated, indicating that at least these chasmata had isolated depositional environments resulting in different stratigraphic sequences. On the other hand, the layered deposits in Ophir-Candor and Melas Chasmata appear to have been connected in each chasma. Some of the layered deposits display complexities which indicate changes in space and time in the dominant source materials.

Komatsu, G.; Geissler, P. E.; Strom, R. G.; Singer, R. B.

1993-06-01

54

Valles Marineris Dune Fields as Seen From the HiRISE, CTX and THEMIS Cameras  

NASA Astrophysics Data System (ADS)

Dune fields on Mars offer an opportunity to investigate the nature of eroded sediments and their interactions with the atmosphere. We examined 20 dune fields in Valles Marineris (VM) from the Mars Global Digital Dune Database [Hayward et al., 2007] to identify significant trends in composition, thermophysical properties, morphology and origin. Dune fields were examined in terms of: slopes, albedo, dust index, thermal inertia and the corresponding derived particle size. We have used image data from the Mars Reconnaissance Orbiter (MRO) instruments CTX [McEwen et al., 2006] and HiRISE [Malin et al., 2007] to establish geologic context for the dune fields, and in particular, to examine their relationships to neighboring geologic units. In general, VM dune fields display greater topographic relief and closer proximity to their inferred source regions than is typical for dune fields elsewhere on Mars. These dunes have a relatively high TES-derived thermal inertia mean value (394 Jm-2K-1 s-1/2, units hereafter assumed), which corresponds to ~1000 ?m grains [Pelkey et al., 2001] or very coarse sand sizes. In contrast, typical non-VM dunes have a lower thermal inertia value of ~250, corresponding to ~350 ?m grains. To investigate this more closely, high-resolution THEMIS-derived thermal inertia maps were created [Putzig et al., 2004]. CTX and HiRISE visible images revealed that bedrock outcrops are commonly found within dune fields, erroneously elevating the TES thermal inertia values over the ~3x5-km TES footprint. However, even after excluding intra-dune outcrop areas using higher-resolution THEMIS data, several VM dune fields have anomalously high thermal inertia values (>500) compared with non-VM dune fields. It is possible that the high thermal inertia values are indicative of indurated (fossilized) dune surfaces, rather than large individual grain sizes. Coprates Chasma contains a concentration of 6 dune fields both within the main chasm and in depressions to the south. The southern fields are comprised of isolated barchanoid dunes, in close proximity to or atop wall material that has been deposited by mass wasting. In the main chasm, previously unidentified barchans composed of large grain sizes, as inferred from THEMIS thermal inertia, are found in CTX images within spur and gully wall units 2-3 km above the canyon floor. TES spectrum of these dunes indicates a basaltic composition, suggesting that the nearby wall units, also thought to be of a basaltic composition [McEwen et al., 1999], could be the source of the dune sediments. Future MRO observations of this area may resolve whether these dune sediments are locally derived. Ganges Chasma has the highest concentration of dunes in VM, including the largest (~6000 km2) non-polar dune field on Mars. These dunes are found surrounding the sulfate-bearing Ganges Mensa and other layered deposits. In one example, a light-toned yardang containing CRISM-detected hydrated sulfates [Pelkey et al., 2007] has shed fans of fine-grained material, contributing sediment to the area. Dune slipface orientation would suggest a dominant wind direction blowing to the west at the last time of dunes activity. This corresponds with the more recent deposit of lighter-toned material down-wind and atop the dark-toned sand sheets, as observed in HiRISE and THEMIS thermal inertia images. These lighter-toned materials, inferred to be composed of sulfate grains (~350 ?m), form bright ripples which gradually disappear away from the yardang. Whether these sulfates constitute a significant percentage of the dune composition is currently under investigation.

Chojnacki, M.; Moersch, J. E.

2008-12-01

55

Putative Large and Small Volcanic Edifices in Valles Marineris, Mars, and Evidence of Ground Water\\/Ice  

Microsoft Academic Search

Large mounds and mesas of interior layered deposits (ILDs) in Valles Marineris Chasmata have been suggested to be sub-ice volcanoes based on MGS and Viking data [1,2,3]. Similar to terrestrial sub-ice volcanoes, spectral investigation indicates the bright mounds are hydrothermally altered, palagonitic rocks [4]. These putative edifices are associated with outcrops of dark materials that have each been interpreted previously

M. G. Chapman; J. L. Smellie

2001-01-01

56

Geomorphological characteristics of the interior layered deposits (ILDs) of Melas Chasma, central Valles Marineris, Mars  

NASA Astrophysics Data System (ADS)

Stretching almost 600 km in width, Melas Chasma is located in the central part of the Valles Marineris (VM) and is one of the lowest lying of the chasmata. Spectral mapping of this chasma, particularly using MEX's OMEGA instrument, has revealed a strong presence of water-altered minerals (roughly a quarter of all such detected minerals to date in the VM; Chojnacki & Hynek, 2008), in the form of monohydrated and polyhydrated sulphates. Most of the sulphate-bearing rocks in Melas are found in association with thinly layered deposits, occurring in outcrops on the chasma floor. So-called interior layered deposits (ILDs) throughout the Valles Marineris have been the subject of considerable recent research, particularly for their association with these water-altered minerals. Better understanding of the origin and evolution of these ILDs may help to shed more light on the past climatic conditions on Mars and the potentially complicated history of liquid water on the planet. Relatively little geomorphological study of the ILDs of Melas Chasma has been conducted to date with regard to the differing characteristics of the different sulphate-bearing rocks. For instance, areas corresponding to polyhydrated sulphates in the Melas ILDs show considerable different surface textures to those corresponding to monohydrated sulphates. Interestingly, the latter show some surface textures comparable to the wind eroded, yardang bearing surfaces of the Medusae Fossae Formation, located roughly 4000 km to the west on the opposite side of the Tharsis volcanic province. This aim of this work, conducted as part of the European Research Council supported eMars project, is to compile a thorough geomorphological survey of the Melas Chasma ILDs and, through this, construct workable hypotheses regarding their origin and evolution and the context of their water-altered mineral content. Furthermore, to contrast and compare the ILDs of Melas with other large-scale deposits, such as the Medusae Fossae Formation and to collate evidence to support Melas Chasma's potential as a suitable landing site for any future martian rover/lander missions.

Harrison, Samantha; Quantin-Nataf, Cathy

2013-04-01

57

Multiple-process origin of Valles Marineris basins and troughs, Mars  

NASA Astrophysics Data System (ADS)

An improved sequence of formation for Valles Marineris depressions is proposed. It involves three key stages; (a) dike emplacement radial to Syria Planum during Late Noachian to Early Hesperian time; (b) localized subsidence of crustal rocks during post-Early Hesperian time, forming ancestral basins such as Hebes Chasma; and (c) regional normal faulting that overprints the ancestral basins and forms the structural troughs, such as Coprates Chasma, principally during Amazonian time. Attainment of high topography at Syria Planum, completed by the Early Hesperian, was accompanied and/or followed by extrusion of ridged plains lavas, emplacement of subsurface dikes, and wrinkle-ridge deformation. The high topography contributed to a substantial hydrostatic head, leading to subsurface volume reduction, vertical displacement of crustal strata to from chaotic terrain and ancestral basins, and localized outbreaks of fluid as outflow channels. The dikes contributed a pervasive structural influence on the orientations of later nearsurface processes. Sometime after infilling of ancestral basins with their interior layered deposits, normal faults related to Tharsis centered stresses were superimposed on the relict high topography, ancestral basins, and dike network, forming large grabens. Recognition of the polygenetic origin of troughs such as Melas Chasma, and the disparate origins of irregular and rectangular troughs, provides the key to unraveling the conflicting accounts of trough origin and timing.

Schultz, Richard A.

1998-06-01

58

Geological and geodynamical studies of the origin and history of the Tharsis and Valles Marineris regions of Mars  

NASA Astrophysics Data System (ADS)

In this thesis I use data from the Mars Global Surveyor (MGS) spacecraft to examine the physical and geological properties of the lithosphere and crust of the Tharsis region of Mars, a vast volcanic and tectonic province. Two geodynamical studies utilize line-of-sight spacecraft accelerations from the Radio Science Experiment and topography from the Mars Laser Orbiter Altimeter (MOLA) for the primary purpose of estimating the effective elastic thickness (Te) for various regions of Tharsis. The value of Te provides temporal and spatial information regarding the formation of crustal features and the values derived in this study are used to infer the evolution of Tharsis over its ˜4.5 billion year history. Thaumasia, the oldest preserved region of Tharsis, is identified in this study as a large corona (a volcanic-tectonic feature identified on Venus). Using corona as an analog, a thin, elastic shell model is developed. Thaumasia is found to be in near-isostatic equilibrium consistent with an ancient formation age. Admittances for three regions of Tharsis are determined and fit with theoretical admittances. From this, Te across Tharsis is inferred to have varied over time and topographic loading appears to have become increasingly confined to the western margin. A photogeologic study of Valles Marineris, a vast canyon system that incises the crust of Tharsis to a depth exceeding 10 km, provides lithologic information regarding the composition of the crust. The rocks that comprise the upper crust of Thaumasia are interpreted to be primarily resulting from effusive flood basalt volcanism and near-surface magmatic intrusion. From these studies, it is concluded that: (1) Tharsis is largely the result of volcanic construction, (2) Thuamasia is the remnant of a large corona-like feature similar to Artemis Corona on Venus and formed within 500 Ma after planetary accretion, (3) volcanic effusion rates were very high during this time with the bulk of Tharsis being emplaced within the first billion years of the planet's history and quickly diminishing thereafter, and (4) volcanic activity has persisted throughout the last ˜3.5 billion years of Martian history in more localized regions confined to the western half of the province.

Williams, Jean-Pierre

59

Comparative Study of 3Dimensional Renderings of the Valles Marineris Interior Layered Deposits on Mars and Terrestrial Sub-Ice Volcanoes in Iceland  

Microsoft Academic Search

A progress report of the current investigation into the interpretation that the Valles Marineris interior layered deposits (ILDs) are analogous to terrestrial sub-ice volcanic forms, such as tuyas and hyaloclastic ridges, by mapping the ILDs and studying analogs in Iceland.

M. G. Chapman; B. K. Lucchitta; I. P. Skilling; J. L. Smellie; T. Thordarson

2003-01-01

60

Multi-sulfate and Iron Oxide Assemblages Within the Valles Marineris Interior Layered Deposits  

NASA Astrophysics Data System (ADS)

MarsExpress OMEGA showed that many of the Interior Layered Deposits (ILDs) in Valles Marineris contain sulfates and proposed the sulfates as indicators of past aqueous activity in the Theiikian period (Gendrin etal, 2005; Bibring etal, 2005; Bibring etal, 2006). Better discrimination of the sulfate assemblages present and the stratigraphic relationships within the ILD is critical to understanding the environment during and since their formation. We present a method for identifying classes of sulfates present in a multi-sulfate exposure with MRO CRISM data. Multiple mineral phases can be defined by diagnostic absorptions in spatially distinct wavelength regions. Combinations of minerals phases is more complicated but can be resolved by identifying superposed absorption feature and assuming linear mixing. We focus on four wavelength regions: (a) 2.4 and 2.1 ?m, (b) 2.2 ?m, (c) 1.9 and 1.4 ?m, and (d) 0.9 ?m, in a methodical classification of possible sulfate types present. While there is some overlap in the wavelength regions, absorptions are sufficiently separate to be recognizable. Additionally, care must be taken to select geologically feasible minerals assemblages. (a) Hydrated sulfates have an absorption near 2.4 um due to probable interactions between the H2O and SO3 molecules (Cloutis etal, 2006). Monohydrated sulfates have a distinct absorption near 2.1 ?m due to combinations of H2O stretch and rotation vibrations of the single water molecule in a sulfate structure (Cloutis etal, 2006) which shifts with cation. Thus minerals such as kieserite (MgSO4 H2O) and szomolnokite (Fe2+SO4 H2O) can be distinguished in CRISM data. (b) The 2.21-2.26 ?m region is generally convex in sulfates, but gypsum (CaSO4 2H2O ) and jarosite group members (MFe3(SO4)2(OH)6) have absorptions there. The minimum within this wavelength region depends on the mineral present. (c)The ~1.9 ?m is due to the OH stretch and H2O bend combination tone and the ~1.4 ?m absorption is due to the 1st overtone of the OH stretch. Sulfates or other minerals with 2+ structural H2O are necessary for the deep water and hydroxyl absorptions in many spectra we observe. (d) Ferric and ferrous minerals have wide absorptions near 0.9 ?m due to charge transfer and electronic transition processes. Presence of a ~0.9 ?m absorption could indicate either a iron-bearing sulfate, a co-existing iron oxide, or both. Ferrous minerals such as olivine and pyroxene can be excluded by the position and width of their 1.0 and 2.0 ?m absorptions. An eastern Candor Chasma ILD has a multiple sulfate assemblage including mono- and polyhydrated sulfates with a variety of cations that are uniform within a specific layer. The sulfates are intimately or spatially mixed on the meter scale. The relative strengths of mono and polyhydrated sulfate absorptions vary with layering, indicating a degree of independence. Mineralogy and geomorphology is consistent with an evaporite sequence or groundwater alteration of ash or aeolian deposits. In addition, iron oxide spectral features overprint the sulfate spectra in some places and cut across layering in others, suggesting the iron-bearing phase may be either separate from the sulfate occurrences or spatially redistributed. Future work will better characterize the assemblage there and in other chasmata ILDs.

Roach, L. H.; Mustard, J. F.; Murchie, S. L.; Bishop, J. L.; Arvidson, R. E.; Morris, R. V.; Milliken, R. E.; Lichtenberg, K. A.

2007-12-01

61

Martian Canyons and African Rifts: Structural Comparisons and Implications.  

National Technical Information Service (NTIS)

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

H. Frey

1978-01-01

62

Coordinating CRISM Observations of Sulfates near Valles Marineris with the Subsurface Bright Salty Soils Exposed in Gusev Crater via Lab Experiments  

Microsoft Academic Search

CRISM has identified unique spectral signatures in inverted channels near Juventae Chasma and other chasmata in the greater Valles Marineris region [1] that are composed of light-toned layered sediments interpreted to be fluvial in origin [2]. These include a weak, broad feature near 1.45 mum, a strong, broad band centered near 1.94 mum, a sharp band at 2.23 mum, and

J. L. Bishop; M. Parente; M. D. Dyar; D. L. Bish; P. Sarrazin; P. King; N. McKeown; R. Milliken; L. Roach; G. Swayze; C. Weitz; S. Murchie; J. F. Mustard

2008-01-01

63

Light-toned deposits in Valles Marineris, on crater bulges, and in chaos: do they have a common origin as spring deposits?  

NASA Astrophysics Data System (ADS)

Layered, massive or mound-shaped light-toned deposits are present at several locations on Mars. They include crater bulges (e.g. Gale), Interior Layered Deposits in Valles Marineris canyon system (e.g. Candor Chasma), bright deposits in chaotic terrains (e.g. Aram Chaos). Despite the differences among these various kinds of deposits and morphologies, they all share some features, such as layering, and a similar topographic setting, i.e. they form bulges in wide topographic depressions (Valles, craters, chaos). Moreover several of these deposits are located in areas where hydrated minerals have been detected (Bibring et al., 2006). The internal architecture of these deposits is often complex, with inclined layering and even angular unconformities. Their size range from few kilometers up to few hundreds generally, with thicknesses from a few hundred meters up to several km (ILD). So far the origin of these deposits has remained enigmatic, although they have been proposed to represent fluvial, lacustrine or volcanic deposits. We suggest chemical precipitation of spring deposits as a possible formation mechanism for several massive, mound-like or layered deposits on Mars. This working hypothesis could explain the co-occurrence of different characteristics in a wide range of deposits: - massive, dome-shaped or well-stratified stacking pattern - horizontal stacking and clinostratification - hiatus in deposition and subsequent erosion of older portion of deposits (e.g. in Gale Crater, of several ILD) - strong lateral facies variations - presence of hydrated minerals - presence of fluvial features closely connected with deposits - location in low areas, where lithostatic pressure could help the fluid expulsion and subsequent buildup - possibility of large buildups due to low gravity - no need for earth-like surface conditions (P, T, precipitation) given groundwater availability On Earth, spring deposits show a wide variety of internal architectures (e.g. Martin-Algarra et al., 2003). Spring deposits have been proposed for small-scale landforms and deposits on Mars (e.g. Crumpler, 2003). We are testing our hypothesis using morphological and spectral information. References: Bibring, J.-P., et al. (2006) Science 312(5772): 400-404. Crumpler, L. S. (2003) Sixth International Conference on Mars. Martin-Algarra, A., M. Martin-Martin, et al. (2003) Sedimentary Geology 161(3-4): 217-228.

Rossi, A.; Neukum, G.; Pondrelli, M.; Zegers, T.; Ori, G.; Hauber, E.; Mason, P.; Chicarro, A.

2006-12-01

64

Composition and structures of the subsurface in the vicinity of Valles Marineris as revealed by central uplifts of impact craters  

NASA Astrophysics Data System (ADS)

Despite recent efforts from space exploration to sound the martian subsurface with RADAR, the structure of the martian subsurface is still unknown. Major geologic contacts or discontinuities inside the martian crust have not been revealed. Another way to analyze the subsurface is to study rocks that have been exhumed from depth by impact processes. The last martian mission, MRO (Mars Reconnaissance Orbiter), put forth a great deal of effort in targeting the central peaks of impact craters with both of its high resolution instruments: CRISM (Compact Reconnaissance Imaging Spectrometer for Mars) and HiRISE (High Resolution Science Experiment). We analyzed the composition with CRISM and the physical characteristics on HiRISE of the rocks exhumed from depth from 31 impact craters in the vicinity of Valles Marineris. Our analyses revealed the presence at depth of two kinds of material: massive light-toned rocks and intact layers. Exhumed light-toned massive rocks are enriched in low calcium pyroxenes and olivine. Hydrated phases such as smectites and putative serpentine are present and may provide evidence of hydrothermal processes. Some of the rocks may represent portions of the volatile-rich, pre-Noachian martian primitive crust. In the second class of central peaks, exhumed layers are deformed, folded, and fractured. Visible-near infrared (VNIR) spectra suggest that they are composed of a mixture of olivine and high calcium pyroxene associated with hydrated phases. These layers may represent a Noachian volcanic accumulation of up to 18 km due to Tharsis activity. The spatial distribution, as well as the in-depth distribution between the two groups of rocks exhumed, are not random and reveal a major geologic discontinuity below the Tharsis lava plateau. The contact may be vertical over several kilometers depth suggesting the pre-existence of a steep basin (early giant impact or subsidence basin) or sagduction processes.

Quantin, Cathy; Flahaut, Jessica; Clenet, Harold; Allemand, Pascal; Thomas, Pierre

2012-09-01

65

Putative Large and Small Volcanic Edifices in Valles Marineris, Mars, and Evidence of Ground Water/Ice  

NASA Astrophysics Data System (ADS)

Large mounds and mesas of interior layered deposits (ILDs) in Valles Marineris Chasmata have been suggested to be sub-ice volcanoes based on MGS and Viking data [1,2,3]. Similar to terrestrial sub-ice volcanoes, spectral investigation indicates the bright mounds are hydrothermally altered, palagonitic rocks [4]. These putative edifices are associated with outcrops of dark materials that have each been interpreted previously as young, volcanic ash deposits of mafic composition [5,6]. Spectral investigation also indicates that the dark materials are less water-altered and mafic in composition [4]. TES-detected concentrations of crystalline hematite have been noted to occur in these dark materials [7]. Mars Observer Camera (MOC) images indicate that the dark materials locally blanket chasmata floors and embay ILDs and are associated with small volcanic vents. These apparent vents may have emitted some of the ash-like deposits. The vent features appear very young, lacking impact craters and having non-eroded rims. Where they embay the ILDs, the vents have low rims similar to terrrestrial maar or tuff cones, which possibly indicates interaction with groundwater or ice. In support of ground-ice within the ILDs, MOC data show (1) channels that occur on the flanks of the bright mounds, and (2) theatre-headed gullies are eroded into caprock of the ILDs and the heads of valleys, formerly interpreted by Viking data to be wind flutes on ILD flanks. Both features may be related to spring sapping. MOC images also show that dark materials on the floor of many chasmata and Aram Chaos are associated with small fissures or cone-shaped mounds with central depressions that do not appear to have interacted with ground-ice. Perhaps late-stage water/ice circulated or was stored within the interior mounds after removal of large ponds of surface ice elsewhere. Young, dark, volcanic ash in the chasmata could be a product of both "dry" volcanism and water/magma interactions, which may have exobiologic implications. References: [1] Croft, S.K., 1990. NASA TM 4210, 539-541. [2] Lucchitta, B.K., N.K. Isbell, A. Howington-Kraus 1994. J. Geophys. Res. 99, 3783-3798. [3] Chapman, M.G. and K.L. Tanaka 2001. J. Geophys. Res. 106, 10,087-10,100. [4] Murchie, S., L. Kirkland, S. Erard, J. Mustard, and M. Robinson 2000 Icarus 147, 444-471. [5] Geissler, P.E., R.B. Singer, and B.K. Lucchitta 1990. J. .Geophys. Res. 95, no. B9, 14,399-14,413. [6] Lucchitta, B.K. 1990. Icarus 86, 476-509. [7] Noreen, E., K.L. Tanaka, and M.G. Chapman 2000. GSA abs. with progs. 32, no. 7, A303.

Chapman, M. G.; Smellie, J. L.

2001-12-01

66

Valles Marineris, Mars: High-Resolution Digital Terrain Model on the basis of Mars-Express HRSC data  

NASA Astrophysics Data System (ADS)

Introduction: Since December 2003, the European Space Agency's (ESA) Mars Express (MEX) orbiter has been investigating Mars. The High Resolution Stereo Camera (HRSC), one of the scientific experiments onboard MEX, is a pushbroom stereo color scanning instrument with nine line detectors, each equipped with 5176 CCD sensor elements. Five CCD lines operate with panchromatic filters and four lines with red, green, blue and infrared filters at different observation angles [1]. MEX has a highly elliptical near-polar orbit and reaches a distance of 270 km at periapsis. Ground resolution of image data predominantly varies with respect to spacecraft altitude and the chosen macro-pixel format. Usually, although not exclusively, the nadir channel provides full resolution of up to 10 m per pixel. Stereo-, photometry and color channels generally have a coarser resolution. One of the goals for MEX HRSC is to cover Mars globally in color and stereoscopically at high-resolution. So far, HRSC has covered almost half of the surface of Mars at a resolution better than 20 meters per pixel. Such data are utilized to derive high resolution digital terrain models (DTM), ortho-image mosaics and additionally higher-level 3D data products such as 3D views. Standardized high-resolution single-strip digital terrain models (using improved orientation data) have been derived at the German Aerospace Center (DLR) in Berlin-Adlershof [2]. Those datasets, i.e. high-resolution digital terrain models as well as ortho-image data, are distributed as Vicar image files (http://www-mipl.jpl.nasa.gov/external/vicar.html) via the HRSCview web-interface [3], accessible at http://hrscview.fu-berlin.de. A systematic processing workflow is described in detail in [4,5]. In consideration of the scientific interest, the processing of the Valles Marineris region will be discussed in this paper. The DTM mosaic was derived from 82 HRSC orbits at approximately -22° S to 1° N and 250° to 311° E. Methods: Apart from the DTM quality, image mosaicking also depends on the quality of exterior orientation data, and in order to generate high resolution DTMs and ortho-images, these data have to be corrected. For this purpose, new exterior and interior orientation data, based on tie-point matching and bundle adjustment have been used. The automated determination of tie points by software provided by the Leibniz Universität Hannover [6] are used as input in the bundle adjustment, provided by the Technische Universität München and Freie Universität Berlin. The bundle adjustment approach for photogrammetric point determination with a three-line camera is a least squares adjustment based on the well known collinearity equations. The approach estimates the parameters of the exterior orientation only at a few selected image lines. Because of Doppler shift measurements to estimate the position of the orbiter there are systematic effects in the observed exterior orientation. To model these effects in the bundle adjustment, additional observation equations for bias (offset) and drift have to be introduced. To use the MOLA DTM as control information, the least squares adjustment has to be extended with an additional observation equation for each HRSC point. These observations describe a relation between the MOLA DTM and these HRSC points. This approach is described in more detail in [7,8]. Derivation of DTMs and ortho-image mosaics are basically performed using software developed at the German Aerospace Center (DLR), Berlin and is using the Vicar environment developed at JPL. For the DTM derivation, the main processing tasks are first a prerectification of image data using the global MOLA-based DTM, then a least-squares area-based matching between nadir and the other channels (stereo and photometry) in a pyramidal approach and finally, DTM raster generation. Iterative low-pass image filtering (Gauss and mean filtering) is applied in order to improve the image matching process by increasing the amount and quality of object points and in order to reduce possible misdetections caused by i

Dumke, A.; Spiegel, M.; van Gasselt, S.; Neukum, G.

2009-04-01

67

Identification and mapping of dikes with relatively primitive compositions in Thaumasia Planum on Mars: Implications for Tharsis volcanism and the opening of Valles Marineris  

NASA Astrophysics Data System (ADS)

We have identified several exposed dikes in Thaumasia Planum Mars using THEMIS, CTX, HiRISE and CRISM data. These dikes extend from tens to ˜100 kilometers in length with average widths of ˜50 m. They display classic ‘en echelon’ patterns while cross-cutting preexisting geologic features, including extensive wrinkle ridges. Both the dikes and associated fissure eruption products have very blocky morphologies with ˜38% higher thermal inertia than the surrounding regions. The dikes are all enriched in Mg-rich olivine relative to surrounding terrain, and a subset also contains elevated high-calcium pyroxene, both of which indicate relatively primitive magma compositions. We propose that these dikes might have served as feeders for the olivine-enriched flood basalts in this region, and may be derived from the Tharsis plume. These observations provide further evidence that the opening of Valles Marineris was facilitated by tectonic stresses following paths of preferential weakness along preexisting structures such as fractures and faults like those indicated by these dikes.

Huang, Jun; Edwards, Christopher S.; Horgan, Briony H. N.; Christensen, Philip R.; Kraft, Michael D.; Xiao, Long

2012-09-01

68

Stratigraphic architectures spotted in southern Melas Chasma, Valles Marineris, Mars  

Microsoft Academic Search

The distribution in space and time of liquid water on Mars is relevant to astrobiology and astroclimatology. To date, most orbital observations that attest to past fluvial and lacustrine activity on Mars have been dedicated to surficial landforms (i.e., drainage networks and depositional fans). Here we report an unprecedented identification of typical stratigraphic architectures made in Mars Global Surveyor Mars

Gilles Dromart; Cathy Quantin; Olivier Broucke

2007-01-01

69

Sulfate Mineral Stratigraphy in Valles Marineris Interior Layered Deposits  

NASA Astrophysics Data System (ADS)

Mineralogic, stratigraphic and tectonic study of exemplar sulfate-rich ILD in E Candor Chasma suggests either a complex evaporite sequence or kieserite formation with later atmospheric alteration to polyhydrated sulfate.

Roach, L. H.; Mustard, J. F.; Murchie, S. L.; Aharonson, O.; Lowenstein, T.; Weitz, C. M.; Arvidson, R. E.; Bishop, J. L.; Lewis, K. W.; Lichtenberg, K.; Seelos, F. P.; CRISM Science Team

2008-03-01

70

Geologic Evidence for Late-Stage Equatorial Surface and Ground Ice on Mars  

Microsoft Academic Search

New imagery data from the Mars Observer Camera suggest that the equatorial canyon of Valles Marineris contained surface and ground ice relatively late in Martian history. Some troughs (or chasmata) of Valles Marineris contain large mounds and mesas of interior layered deposits (ILDs) that formed in the Late Hesperian to Early Amazonian. Although the origin of the ILDs remains controversial,

M. G. Chapman

2003-01-01

71

Duration and rates of discharge - Maja Valles, Mars  

Microsoft Academic Search

The 1600 km-long Maja Valles outflow system of Mars consists of three major divisions including the upper valley on Lunae Planum, the canyon section across Xanthe Terra, and the lower valley across western Chryse Planitia. Although water released from the source in Juventae Chasma could reach the terminus of the present day valley system in central Chryse Planitia within 44

R. A. de Hon; E. A. Pani

1993-01-01

72

Constraints on the Rate of Sulfate Phase Changes in Valles Marineris Interior Layered Deposits  

NASA Astrophysics Data System (ADS)

Spectral and geomorphic interpretations of two multiple-sulfate bearing ILDs suggest either exposure of a diverse sulfate evaporite sequence or recent, dynamic hydration of kieserite. Paired OMEGA and CRISM data spaced one year apart constrain rate.

Roach, L. H.; Mustard, J. F.; Murchie, S. L.; Bibring, J.-P.; Arvidson, R. E.; Bishop, J. L.; Milliken, R. E.; Seelos, F. P.; CRISM Science Team

2008-03-01

73

Sulfate Identification in East Candor, Valles Marineris with CRISM Visible-Infrared Spectra  

NASA Astrophysics Data System (ADS)

Joint CRISM-HiRISE analysis of kieserite and polyhydrated sulfates within light-toned deposits in East Candor reveal alternating occurrences. Interpretations include interbedding of mono- and polyhydrated sulfates or post-exposure phase change.

Roach, L. H.; Mustard, J. F.; Murchie, S.; Weitz, C. M.; Ehlmann, B. L.; Pelkey, S.; Seelos, F. P.; Seelos, K.; Bibring, J.-P.; CRISM Team

2007-03-01

74

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."

75

Discontinuities in the shallow Martian crust at Lunae, Syria, and Sinai Plana  

Microsoft Academic Search

Detailed photoclinometric profiles across 125 erosional features and 141 grabens in the western equatorial region of Mars indicate the presence of three discontinuities within the shallow crust. Pits, troughs, and wall valleys (tributary canyons) within Noctis Layrinthus and Valles Marineris and escarpments within the fretted terrain of Sacra Fossae and Kasei Valles show distinct erosional base levels at depths of

Philip A. Davis; Matthew P. Golombek

1990-01-01

76

Variation of the 3-mum absorption feature on Mars: Observations over eastern Valles Marineris by the Mariner 6 infrared spectrometer  

Microsoft Academic Search

A new approach for calibration of the shortest wavelength channel (1.8 to 6.0 mum) of the Mariner 6 infrared spectrometer was derived. This calibration provides a new description of the instrument response function from 1.8 to 3.7 mum and accounts for the thermal contribution to the signal at longer wavelengths. This allows the two segments from 1.8 to 6 mum

Wendy M. Calvin

1997-01-01

77

Valles Caldera research opportunity  

NASA Astrophysics Data System (ADS)

Drilling has been completed at Valles Caldera, N.M., as part of the Continental Scientific Drilling Program (CSDP). The team reports that objectives of the drill (Eos, August 14, 1984, p. 474) were met: approximately 168 m of obsidian, several geothermal aquifers, and structural and stratigraphic information, plus widespread hydrothermal alterations, one oriented core, and a suite of geophysical logs. The well now is cased for future research and geochemical sampling.The well was drilled to a total depth of 856 m, and an unequilibrated bottom hole tem-perature of 160°C was reached. Core recovery is reported at better than 95%. Hydrothermal alterations include clays, calcite, quartz, pyrite, and chlorite from the volcanic colluvium down to total depth. The intensity of alteration increases with depth and/or along major fractures and faults.

78

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

79

Valles Caldera workshop  

NASA Astrophysics Data System (ADS)

A Continental Scientific Drilling Project (CSDP) Workshop, attended by 87 scientists, focusing on the Valles caldera was hosted by the Department of Energy and the Los Alamos National Laboratory, on October 5-7, 1982, in Los Alamos, New Mexico. The caldera, a large, Quaternary magmahydrothermal system, lies at the intersection of the Rio Grande rift and the Jemez lineament in north-central New Mexico and is a prime site for the first deep drill holes.One major objective of CSDP is to develop a broad scientific understanding of the roots of an active hydrothermal system associated with recent igneous intrusion. Surface geological, geophysical, geochemical, and hydrological data, along with information from shallow exploratory drillholes, will be used in the process of interactive development and testing of models and hypotheses for such systems. Ultimately, deep drilling will be essential to provide direct sampling of fluids and rocks at depth and to measure directly the critical in situ physical parameters. Thus, deep drilling research becomes an integral and necessary component in the synthesis, refinement, and verification of three-dimensional models of hydrothermal-magma systems and processes.

Riecker, Robert E.

80

Mars  

NSDL National Science Digital Library

The true global geography of Mars first emerged with comprehensive maps from Mariner 9 and Viking during the 1970s. This visualization tours the Red Planet using the Viking dataset, hitting such features as the Valles Marineris canyons and the Olympus Mons volcano.

Crippen, Robert; Curkendall, Dave; Jacob, Joseph; Li, Peggy; Plesea, Lucian; Pomerantz, Marc

1999-01-21

81

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.

82

Adventures in Glen Canyon.  

National Technical Information Service (NTIS)

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

1994-01-01

83

Ancient Observatories: Chaco Canyon  

NSDL National Science Digital Library

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

2009-03-12

84

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

85

Currents in Monterey Submarine Canyon  

Microsoft Academic Search

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

J. P. Xu; Marlene A. Noble

2009-01-01

86

Grand Canyon Explorer: The Geology of the Grand Canyon  

NSDL National Science Digital Library

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

Ribokas, Bob

87

New York Canyon Stimulation  

SciTech Connect

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

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

2012-06-21

88

John Wesley Powell, Canyon Geologist.  

National Technical Information Service (NTIS)

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

1994-01-01

89

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.

90

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.

91

Academy of the Canyons Report, Fall 2002.  

ERIC Educational Resources Information Center

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

Meuschke, Daylene M.; Gribbons, Barry C.

92

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

PubMed

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

Baratian-Ghorghi, Z; Kaye, Nigel B

2012-11-23

93

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

94

A GEOLOGICAL AND GEOPHYSICAL STUDY OF THE BACA GEOTHERMAL FIELD, VALLES CALDERA, NEW MEXICO  

SciTech Connect

The Baca location {number_sign}1 geothermal field is located in north-central New Mexico within the western half of the Plio-Pleistocene valles Caldera. Steam and hot water are produced primarily from the northeast-trending Redondo Creek graben, where downhole temperatures exceed 500 F. Stratigraphically the reservoir region can be described as a five-layer sequence that includes (1) caldera fill and the upper units of the Bandelier ash flow tuff, (2) the lower members of this tuff, which comprise the main reservoir rock at Baca, (3) the Pliocene Paliza Canyon volcanics, (4) Tertiary sands and Paleozoic sedimentary rocks, and (5) Precambrian granitic basement. Production is controlled by fractures and faults that are ultimately related to activity in the Rio Grande Rift system. Geophysically, the caldera is characterized by a gravity minimum and a resistivity low. A 40-mgal gravity minimum over the caldera is due mostly to the relatively low-density volcanics and sediments that fill the caldera and probably bears no relation to deep-seated magmatic sources. Two-dimensional gravity modeling indicates that the depth to Precambrian basement in Redondo Canyon is probably at least 3 km and may exceed 5 km in eastern parts of the caldera. Telluric and magnetotelluric surveys have shown that the reservoir region is associated with low resistivity and that a deep low-resistivity zone correlates well with the depth of the primary reservoir inferred from well data.

Wilt, M.; Haar, S.V.

1982-03-01

95

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

National Technical Information Service (NTIS)

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

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

1997-01-01

96

Megabreccias, Early Lakes, and Duration of Resurgence Recorded in Valles Caldera, New Mexico  

NASA Astrophysics Data System (ADS)

New 1:24,000 scale geologic mapping combined with previous and ongoing geoscientific studies are revealing significant new findings on intracaldera stratigraphy and structure, initial development of intracaldera lakes, and the duration of resurgence within the ca. 1.25 Myr Valles caldera. The caldera is about 22 km in diameter and contains a resurgent dome that is a northeast-trending oval roughly11 x 9 km in dimension. Maximum resurgence (uplift) was more than 1000 m, during which the dome split into three principal segments herein named the Redondo Peak, Redondo Border, and Valle San Luis segments. These segments are separated from each other by long, narrow grabens herein called the Redondo Creek, Jaramillo Creek, and San Luis Creek grabens. Differential uplift accompanied by intense faulting has exposed large, rootless megabreccia (Mbx) blocks composed of precaldera rocks submerged in densely welded, intracaldera upper Bandelier Tuff. The largest Mbx blocks are roughly 0.2 to 2.0 km long and consist primarily of Abo Fm (Permian), Gallisteo Fm (?) (Eocene), Santa Fe Group (Miocene), Paliza Canyon Fm (late Miocene) and lower Bandelier Tuff (ca. 1.62 Ma). Deep geothermal wells drilled within the Redondo Creek graben from 1970 to 1983 penetrate as much as 2032 m of intracaldera Bandelier Tuff and post-Bandelier rocks before intersecting caldera floor rocks (average = 1646 m, n = 23 wells). Evidence that a lake developed within the caldera depression is preserved in finely laminated lacustrine beds and rhyolitic, hydromagmatic tuffs that overlie intracaldera Bandelier Tuff on the resurgent dome. The lacustrine rocks contain organic remains and the hydromagmatic tuffs contain accretionary lapilli. In some locations, lacustrine and hydromagmatic rocks are interbedded. Earliest post-caldera rhyolite lavas (Deer Canyon Member) display occasional pepperite and pillow textures. Many lavas contain significant amounts of fine, opalized flow breccia indicating interaction with water. Associated Deer Canyon tuffs are altered to variable mixtures of silica, smectite, clinoptilolite, mordenite and other phases. Slightly younger rhyolite lava flows (Redondo Creek Member) occasionally display upper flow surfaces in which cracks are filled with zeolitized mud. The combined geologic evidence indicates that the initial Valles lake was widespread and relatively shallow, containing waters with neutral to alkaline pH and relatively high K/Na ratios. 40Ar/39Ar dating of sanidine separates from Deer Canyon and Redondo Creek rhyolites yields ages that are statistically indistinguishable from the age of underlying upper Bandelier Tuff. These results indicate that the intracaldera lake developed immediately after the caldera formed and that the resurgent dome rose out of a lake. Most resurgence occurred after Redondo Creek rhyolite was erupted because the unit is intensely faulted and associated lacustrine beds are now as much as 500 m above the undeformed caldera moat. In contrast, rhyolite lavas of the first post-caldera moat complex, Cerro del Medio (about 1.22 Ma) show no apparent deformation or uplift due to resurgence. Within the errors of the various 40Ar/39Ar dates, the apparent duration of resurgence was no longer than about 50,000 years yielding a minimum resurgence rate of about 2 cm/y.

Goff, F.; Goff, C. J.; Phillips, E. H.; Kyle, P. R.; McIntosh, W. C.; Chipera, S.; Gardner, J. N.

2003-12-01

97

Geomorphology of continental slope canyons  

NASA Astrophysics Data System (ADS)

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

Mitchell, N. C.

2006-12-01

98

36 CFR 7.70 - Glen Canyon National Recreation Area.  

Code of Federal Regulations, 2010 CFR

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

2010-07-01

99

36 CFR 7.70 - Glen Canyon National Recreation Area.  

Code of Federal Regulations, 2010 CFR

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

2009-07-01

100

77 FR 9265 - Glen Canyon Dam Adaptive Management Work Group  

Federal Register 2010, 2011, 2012, 2013

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

2012-02-16

101

78 FR 7810 - Glen Canyon Dam Adaptive Management Work Group  

Federal Register 2010, 2011, 2012, 2013

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

2013-02-04

102

76 FR 24516 - Glen Canyon Dam Adaptive Management Work Group  

Federal Register 2010, 2011, 2012, 2013

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

2011-05-02

103

78 FR 21415 - Glen Canyon Dam Adaptive Management Work Group  

Federal Register 2010, 2011, 2012, 2013

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

2013-04-10

104

77 FR 22801 - Glen Canyon Dam Adaptive Management Work Group  

Federal Register 2010, 2011, 2012, 2013

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

2012-04-17

105

77 FR 43117 - Glen Canyon Dam Adaptive Management Work Group  

Federal Register 2010, 2011, 2012, 2013

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

2012-07-23

106

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

ERIC Educational Resources Information Center

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

Dixon, P. Scott; Gribbons, Barry C.

107

Third hole planned at Valles Caldera  

NASA Astrophysics Data System (ADS)

Valles caldera, N. Mex., is the culmination of more than 13 million years of volcanism in the Jemez volcanic field and is an excellent model for resurgent calderas and for the high-temperature geothermal systems found with them. This month one of the biggest diamond drills in the world will start the third research core hole in the caldera. Valles Caldera 2B will be the tenth core hole in the Department of Energy's Continental Scientific Drilling Program.CSDP drilling in the 1.1-million-year-old caldera began in 1984 in the southwest moat zone when the research hole Valles Caldera 1 was continuously cored to 856 m. VC-1 intersected a hydrothermal outflow plume from the deep geothermal system. Data indicate multiple episodes of hydrothermal activity in the volcanic field's history, as well as multiple episodes of rhyolite magma generation during evolution of the caldera. The June 10, 1988 (vol. 63), issue of Journal of Geophysical Research—Solid Earth and Planets carried a special section on results from VC-1.

Gardner, Jamie

108

Juventae Chasma and Maja Valles, Mars: Further Evidence for Multiple Flooding Events  

NASA Astrophysics Data System (ADS)

Introduction: In this study we investigate the age relationship of Juventae Chasma to the adjacent Maja Valles in order to gain a feasible explanation for the formation and evolution of rhythmic light-toned layered deposits (LLD). In this first step, we use impact crater size-frequency distributions for dating the planetary surface in the regions of interest. Juventae Chasma is located at the northern side of the Valles Marineris and stretches for approximately 150 km east-west and 250 km north-south. The basin floor shows a depth of 5 km and more below the surrounding surface. To the north lies the adjacent Maja Valles, a 50 km to 150 km wide channel extending for 1600 km northward and discharging into the Chryse Planitia plains. Various investigations of several authors have been carried out on this subject in the past, but the formation of the LLD in Juventae Chasma is still poorly understood. The formation theories range from a volcanic origin [1], lake deposits, delta deposits [2] to spring deposits [3]. A very different hypothesis for the formation of the sulfates is deposition from airfall. This could happen as dry deposition from the atmosphere or in co-precipitation with icy materials such as snow crystals or dust particles. This phenomenon is observed at the poles of Mars, where rhythmic layerings occur showing high similarities to the sulfate deposits in Juventae Chasma. The light-toned materials in the chasma show a spectral signature indicative of kieserite in the outcrops A, C and D and in the lower part of B, whereas the upper part of B was described as gypsum [4]. Wendt et al. [5] identified different mineral assemblages in the cap rock of mount B, using the CRISM instrument and the Multiple-Endmember Linear Spectral Unmixing Model (MELSUM). HRSC DTM: The Digital Terrain Model (DTM ) mosaic (see Fig. 1) was derived from 11 HRSC orbits at approximately -7° S to 8° N and 295° to 301° E with a ground resolution of 100 m per pixel and an ortho-image mosaic with a ground resolution of 12.5 m per pixel. The main processing tasks for the DTM derivation are first a pre-rectification of image data using the global MOLA- based DTM, then a least-squares area-based matching between nadir and the other channels (stereo and photometry) in a pyramidal approach and finally, DTM raster generation. Improved orientation data are necessary for high-resolution digital terrain models and orthoimage mosaics. For this purpose, new exterior and interior orientation data, based on tie-point matching have been used. The bundle adjustment approach for photogrammetric point determination with a three-line camera is a least squares adjustment based on the well known collinearity equations [6]. The construction of the HRSC-DTM is the basis for further investigation of the masses and volumes, transported from Juventae Chasma through Maja Valles. We use HRSC and OMEGA (Mars Express), as well as HiRise and CRISM (Mars Reconnaissance Orbiter) data for generally mapping the target area. Crater counting is carried out using CTX and HRSC images. Results: The results of the first determinations of the impact crater size-frequency distributions are presented in Fig. 2 and 3 and show an age of 1.22 Ga (+/- 0.16 Ga) for the western part of the Maja Valles channel. The southeastern channel (close to the streamlined island) shows older ages of 3.68 Ga (+0.08/-0.17 Ga) and 2.18 Ga (+/- 0.31 Ga). This clearly indicates, that multiple flooding events took place in the area. The first results for Juventae Chasma age determinations indicate an age of 3.33 Ga. Conclusions: The HRSC-DTM enables us to examine the study area most accurately. We dated the formation of the Juventae Chasma with an age of at least 3.33 Ga. The investigated sites at Maja Valles clearly show evidences for multiple outflow events. Some of these events took place before the formation of the sulfate deposits in Juventae Chasma. Further age determinations and mapping will be carried out in this area to obtain a chronology of events of this highly interesting area in the equatoria

Gross, C.; Wendt, L.; Dumke, A.; Neukum, G.

2009-04-01

109

Seismic modeling of the Valles caldera, Jemez Mountains, New Mexico  

Microsoft Academic Search

This study presents results from seismic modeling of the Valles caldera complex, Jemez Mountains, northern New Mexico, from refraction\\/wide-angle reflection data acquired during the Jemez Tomography Experiment (JTEX) in 1993 and 1995. Data from three seismic profiles were collected and modeled and results are presented here. These data are centered on the Valles caldera, a silicic volcanic system with active

Mark Edward Davidson

2000-01-01

110

Satellites See Smoke from Fourmile Canyon Fire  

NASA Video Gallery

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

gsfcvideo

2010-09-08

111

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

112

Upper Los Alamos canyon fact sheet  

Microsoft Academic Search

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

Jeffrey H

2007-01-01

113

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

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

114

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

115

History of the youngest members of the Valles Rhyolite, Valles Caldera, New Mexico using ESR dating method.  

National Technical Information Service (NTIS)

The cooling history of the Valles caldera was studied by the electron spin resonance (ESR) dating method using Al and Ti centers in quartz grains which were separated from the youngest units of the Valles Rhyolite. The ESR apparent ages are much younger t...

K. Ogoh S. Toyoda S. Ikeda M. Ikeya F. Goff

1991-01-01

116

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

117

The Grand Canyon: How It Formed  

NSDL National Science Digital Library

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

2011-02-23

118

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.

119

Grassland in the Valle Grande, Valles Caldera National Preserve, New Mexico, near sunrise.  

NSDL National Science Digital Library

The Valle Grande in the Valles Caldera National Preserve, New Mexico is one of the National Science FoundationÃÂs Ecology of Infectious Disease study sites. A recent study examined the role that local environmental changes play in deer mouse (Peromyscus maniculatus) and Sin Nombre virus distributions. Hantavirus Pulmonary Syndrome (HPS) is a human disease caused by infection with hantaviruses, which are maintained in rodent populations. HPS was recognized following an outbreak of pulmonary disease among humans in the U.S. Southwest in 1993, and infection with Sin Nombre virus (SNV) was traced to its reservoir, the deer mouse. The number of HPS cases varies both geographically and among years, and it has been hypothesized that the variation reflects environmental changes that affect rodent populations. This photograph originally appeared on the cover of Ecological Applications (17:1) in February of 2007.

Norris, Douglas E.

2010-02-15

120

Modelling Aerosol Dispersion in Urban Street Canyons  

NASA Astrophysics Data System (ADS)

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

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

2009-04-01

121

Walnut Canyon National Monument: An Archeological Overview.  

National Technical Information Service (NTIS)

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

P. A. Gilman

1976-01-01

122

Solar Filament Eruption Creates 'Canyon of Fire'  

NASA Website

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

123

Flow dynamics of a wide Arctic canyon  

NASA Astrophysics Data System (ADS)

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

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

1997-08-01

124

Different Views of the Grand Canyon  

NASA Astrophysics Data System (ADS)

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

Elders, Wilfred A.

125

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

126

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

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

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

127

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

128

36 CFR 7.92 - Bighorn Canyon National Recreation Area.  

Code of Federal Regulations, 2013 CFR

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

2013-07-01

129

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

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

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

130

Geologic Map of the Valles Caldera, Jemez Mountains, New Mexico  

NASA Astrophysics Data System (ADS)

Valles caldera is famous as the type locality of large resurgent calderas (Smith and Bailey, 1968), the location of a classic 260-300 °C liquid-dominated geothermal system (Goff and Gardner, 1994), and the site of a long-lived late Pleistocene lake (Fawcett et al., 2011). We have published a detailed color geologic map of the Valles caldera and surrounding areas at 1:50,000 scale obtainable from New Mexico Bureau of Geology and Mineral Resources (geoinfo.nmt.edu/publications/maps/geologic/gm/79/). The new Valles map has been compiled from all or parts of nine 1:24,000 geologic maps completed between 2004 and 2008 (Bland, Cerro del Grant, Jarosa, Jemez Springs, Polvadera Peak, Redondo Peak, Seven Springs, Valle San Antonio, and Valle Toledo). Our map provides more detailed geology on the resurgent dome, caldera collapse breccias, post-caldera lava and tuff eruptions, intracaldera sedimentary and lacustrine deposits, and precaldera volcanic and sedimentary rocks than previous maps and incorporates recent stratigraphic revisions to the geology of the Jemez Mountains volcanic field. Three cross sections supported by surface geology, geophysical data and deep borehole logs (?4500 m) show an updated view of the caldera interior, depict a modern interpretation of caldera collapse and resurgence, and provide caldera-wide subsurface isotherms (?500 °C). A 30 page booklet included with the map contains extensive rock descriptions for 162 stratigraphic units and figures showing physiographic features, structural relations between Valles (1.25 Ma) and the earlier, comparably sized Toledo caldera (1.62 Ma), correlation charts of map units, and the distribution of pre- and post-caldera hydrothermal alteration styles, including recently documented zeolite-type alteration. Finally, the booklet includes a generalized model showing our interpretation of intracaldera structure and subjacent magma chambers, and relations of Valles to earlier Quaternary-Precambrian units.

Goff, F.; Gardner, J. N.; Reneau, S. L.; Kelley, S. A.; Kempter, K. A.; Lawrence, J. R.

2011-12-01

131

Dispersion Mechanisms In A Street Canyon.  

NASA Astrophysics Data System (ADS)

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

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

132

Recreational impacts on Colorado River beaches in Glen Canyon, Arizona  

Microsoft Academic Search

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

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

1984-01-01

133

36 CFR 7.4 - Grand Canyon National Park.  

Code of Federal Regulations, 2010 CFR

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

2010-07-01

134

36 CFR 7.4 - Grand Canyon National Park.  

Code of Federal Regulations, 2010 CFR

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

2009-07-01

135

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

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

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

136

Air Pollution Optimal Traffic Control in Integrated Street Canyons  

Microsoft Academic Search

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

A. Adamski; M. M. Duras

137

75 FR 34476 - Glen Canyon Dam Adaptive Management Work Group  

Federal Register 2010, 2011, 2012, 2013

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

2010-06-17

138

The Grand Canyon: Its Youngest Rocks  

NSDL National Science Digital Library

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

2011-03-14

139

Geology Fieldnotes: Bryce Canyon National Park, Utah  

NSDL National Science Digital Library

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

Foos, Annabelle

140

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.

141

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

SciTech Connect

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

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

1980-12-01

142

Athabasca Valles, Mars: a lava-draped channel system.  

PubMed

Athabasca Valles is a young outflow channel system on Mars that may have been carved by catastrophic water floods. However, images acquired by the High-Resolution Imaging Science Experiment camera onboard the Mars Reconnaissance Orbiter spacecraft reveal that Athabasca Valles is now entirely draped by a thin layer of solidified lava-the remnant of a once-swollen river of molten rock. The lava erupted from a fissure, inundated the channels, and drained downstream in geologically recent times. Purported ice features in Athabasca Valles and its distal basin, Cerberus Palus, are actually composed of this lava. Similar volcanic processes may have operated in other ostensibly fluvial channels, which could explain in part why the landers sent to investigate sites of ancient flooding on Mars have predominantly found lava at the surface instead. PMID:17885126

Jaeger, W L; Keszthelyi, L P; McEwen, A S; Dundas, C M; Russell, P S

2007-09-21

143

Hydrothermal alteration in the Baca Geothermal System, Redondo Dome, Valles Caldera, New Mexico  

NASA Astrophysics Data System (ADS)

Thermal fluids circulating in the active hydrothermal system of the resurgent Redondo dome of the Valles caldera have interacted with their diverse host rocks to produce well-zoned alteration assemblages, which not only help locate permeable fluid channels but also provide insight into the system's thermal history. The alteration shows that fluid flow has been confined principally to steeply dipping normal faults and subsidiary fractures as well as thin stratigraphic aquifers. Permeability along many of these channels has been reduced or locally eliminated by hydrothermal self-sealing. Alteration from the surface through the base of the Miocene Paliza Canyon Formation is of three distinctive types: argillic, propylitic, and phyllic. Argillic alteration forms a blanket above the deep water table in formerly permeable nonwelded tuffs. Beneath the argillic zone, pervasive propylitic alteration is weakly developed in felsic host rocks but locally intense in deep intermediate composition volcanics. Strong phyllic alteration is commonly but not invariably associated with major active thermal fluid channels. Phyllic zones yielding no fluid were clearly once permeable but now are hydrothermally sealed. High-temperature alteration phases at Baca are presently found at much lower temperatures. We suggest either that isotherms have collapsed due to gradual cooling of the system, that they have retreated without overall heat loss due to uplift of the Redondo dome, that the system has shifted laterally, or that it has contracted due to a drop in the water table. The deepest Well (B-12, 3423 m) in the dome may have penetrated through the base of the active hydrothermal system. Below a depth of 2440 m in this well, hydrothermal veining largely disappears, and the rocks resemble those developed by isochemical thermal metamorphism. The transition is reflected by temperature logs, which show a conductive thermal gradient below 2440 m. This depth may mark the dome's neutral plane, which separates an upper permeable zone of extensional fracturing from a lower, less permeable compressional regime. The Baca hydrothermal system is similar to those which have formed ore deposits in other calderas: particularly, Creede (Colorado) type epithermal silver base metal veins and stockworks. Recent scientific drilling has also intersected a deep zone of strong phyllic alteration and molybdenum mineralization in the Valles caldera's ring fracture system, a setting which localized a large stockwork molybdenite orebody in the nearby Questa caldera.

Hulen, Jeffrey B.; Nielson, Dennis L.

1986-02-01

144

Resonant amplification of subinertial tides in a submarine canyon  

NASA Astrophysics Data System (ADS)

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

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

2011-09-01

145

Recreational impacts on Colorado River beaches in Glen Canyon, Arizona  

NASA Astrophysics Data System (ADS)

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

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

1984-07-01

146

The Colorado River in the Grand Canyon.  

ERIC Educational Resources Information Center

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

Speece, Susan

1991-01-01

147

Bowen Canyon Bald Eagle Sanctuary: An Overview.  

National Technical Information Service (NTIS)

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

C. Ketchum

1985-01-01

148

77 FR 48151 - Boulder Canyon Project  

Federal Register 2010, 2011, 2012, 2013

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

2012-08-13

149

78 FR 48670 - Boulder Canyon Project  

Federal Register 2010, 2011, 2012, 2013

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

2013-08-09

150

Mt. Vernon Canyon Runaway Truck Escape Ramp.  

National Technical Information Service (NTIS)

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

R. L. Hayden

1982-01-01

151

Different Views of the Grand Canyon  

Microsoft Academic Search

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

Wilfred A. Elders

2003-01-01

152

Workshop on recent research in the Valles caldera  

SciTech Connect

Over the last 5 years, there has been increased interest in the geology of the Jemez Mountains volcanic field, New Mexico. Of special interest is the Toledo-Valles caldera complex, which is targeted for research coring as part of the Continental Scientific Drilling Program. The general topics covered in this workshop were (1) hydrothermal systems and rock-water interactions, (2) volcanology and structural framework of the Jemez volcanic field, (3) determining the presence or absence of melt below the Valles caldera, and (4) deep coring and drilling technology. Separate abstracts were prepared for each presentation.

Heiken, G. (comp.)

1985-02-01

153

Creationism in the Grand Canyon, Texas Textbooks  

NASA Astrophysics Data System (ADS)

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

Folger, Peter

2004-01-01

154

Big Canyon Creek Ecological Restoration Strategy.  

SciTech Connect

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

Rasmussen, Lynn; Richardson, Shannon

2007-10-01

155

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

Microsoft Academic Search

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

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

2009-01-01

156

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

Microsoft Academic Search

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

Hill Pj; P. De Deckker; Exon Nf

2005-01-01

157

On the origin of the Andoya Canyon of Norway  

NASA Astrophysics Data System (ADS)

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

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

2003-04-01

158

Land- and Resource-Use Issues at the Valles Caldera.  

National Technical Information Service (NTIS)

The Valles Caldera possesses a wealth of resources from which various private parties as well as the public at large can benefit. Among the most significant of these are the geothermal energy resource and the natural resource. Wildlife, scenic, and recrea...

P. R. Intemann

1981-01-01

159

Sedimentary processes in the middle Nazaré Canyon  

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

160

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

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

161

Grand Canyon Monitoring and Research Center  

NSDL National Science Digital Library

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

162

Holocene vegetation in chaco canyon, new Mexico.  

PubMed

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

Betancourt, J L; VAN Devender, T R

1981-11-01

163

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

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

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

164

Wind fields and turbulence statistics in an urban street canyon  

Microsoft Academic Search

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

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

2006-01-01

165

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

Federal Register 2010, 2011, 2012, 2013

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

2012-02-06

166

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

Code of Federal Regulations, 2013 CFR

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

2013-07-01

167

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

Code of Federal Regulations, 2010 CFR

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

2010-07-01

168

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

Code of Federal Regulations, 2010 CFR

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

2009-07-01

169

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

Federal Register 2010, 2011, 2012, 2013

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

2010-04-19

170

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

Federal Register 2010, 2011, 2012, 2013

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

2013-09-04

171

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

Federal Register 2010, 2011, 2012, 2013

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

2011-01-05

172

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

Federal Register 2010, 2011, 2012, 2013

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

2010-01-05

173

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

Federal Register 2010, 2011, 2012, 2013

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

2010-07-29

174

Transfer processes in a simulated urban street canyon  

NASA Astrophysics Data System (ADS)

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

Solazzo, E.; Britter, R. E.

2007-07-01

175

A natural analogue for high-level waste in tuff: Chemical analysis and modeling of the Valles site  

SciTech Connect

The contact between an obsidian flow and a steep-walled tuff canyon was examined as an analogue for a high-level waste repository. The analogue site is located in the Valles Caldera in New Mexico, where a massive obsidian flow filled a paleocanyon in the Battleship Rock Tuff. The obsidian flow provided a heat source, analogous to waste panels or an igneous intrusion in a repository, and caused evaporation and migration of water. The tuff and obsidian samples were analyzed for major and trace elements and mineralogy by INAA, XRF, x-ray diffraction, and scanning electron microscopy and electron microprobe. Samples were also analyzed for D/H and {sup 39}Ar/{sup 40}Ar isotopic composition. Overall, the effects of the heating event seem to have been slight and limited to the tuff nearest the contact. There is some evidence of devitrification and migration of volatiles in the tuff within 10 m of the contact, but variations in major and trace element chemistry are small and difficult to distinguish from the natural (pre-heating) variability of the rocks.

Stockman, H.W.; Krumhansl, J.L.; Ho, C.K. [Sandia National Labs., Albuquerque, NM (United States); Kovach, L. [US Nuclear Regulatory Commission, Washington, DC (United States); McConnell, V.S. [Univ. of Alaska, Fairbanks, AK (United States)

1995-03-01

176

Land- and resource-use issues at the Valles Caldera  

SciTech Connect

The Valles Caldera possesses a wealth of resources from which various private parties as well as the public at large can benefit. Among the most significant of these are the geothermal energy resource and the natural resource. Wildlife, scenic, and recreational resources can be considered components of the natural resource. In addition, Native Americans in the area value the Valles Caldera as part of their religion. The use of land in the caldera to achieve the full benefits of one resource may adversely affect the value of other resources. Measures can be taken to minimize adverse affects and to maximize the benefits of all the varied resources within the caldera as equitably as possible. An understanding of present and potential land and resource uses in the Caldera, and who will benefit from these uses, can lead to the formulation of such measures.

Intemann, P.R.

1981-01-01

177

Core log: Valles caldera No. 2A, New Mexico  

SciTech Connect

Scientific core hole VC-2A was drilled into the western ring-fracture zone at Sulphur Springs in the Valles caldera, New Mexico. VC-2A, the second scientific core hole in the caldera, was cored through a faulted and brecciated sequence of intracauldron tuffs and volcaniclastic rocks to a depth of 528 m. As of November 1, 1986, the unequilibrated bottom-hole temperature was 212/degree/C. The rocks penetrated are intensely altered and host sub-ore grade stockwork molybdenite mineralization between 25 and 125 m. This report contains a detailed core log to aid researchers in their studies of the Valles caldera magma hydrothermal system. 3 refs., 2 figs.

Starguist, V.L.

1988-01-01

178

Variation of Fracturing Pressures with Depth Near the Valles Caldera  

Microsoft Academic Search

Hydraulic Fracturing at the Fenton Hill Hot Dry Rock Geothermal site near the Valles Caldera has yielded fracturing pressures from 14 to 81 MPa (2030 to 11,750 psi) at depths ranging from 0.7 to 4.4 km (2250 to 14,400 ft). This data can be fit to a fracture gradient of 19 MPa\\/km (0.84 psi\\/ft), except for an anomalous region between

Zora Dash; Hugh Murphy

1983-01-01

179

Continental Scientific Drilling Program: Valles Caldera, New Mexico  

SciTech Connect

The U.S. Continental Scientific Drilling Program attempts to develop a better understanding of the geologic and hydrologic mechanisms within the continental crust, under the auspices of an interagency group comprising the US Department of Energy, the National Science Foundation, and the U.S. Geological Survey. Ten years of research and drilling in the Valles caldera of northern New Mexico has provided a new understanding of volcanism and geothermal systems within a large caldera. Situated at the intersection of the Rio Grande rift and the Jemez volcanic lineament, the Valles caldera and Toledo calderas were formed during two massive eruptions 1.1 and 1.5 M a that vented approximately 300 to 400 km{sup 3} of high-silica rhyolitic tephra. The research at the Valles/Toledo caldera has provided more than 3000 m of corehole samples, which are stored in a repository in Grand Junction, Colorado, and are accessible to the public. This research has also helped support theories of mineral deposition within hydrothermal systems-hot water circulating through breccias, leaching elements from the rocks, and later depositing veins of economically valuable materials.

None

1993-01-01

180

Adobe unlocks Cherry Canyon, other zones in prolific Barstow unit  

Microsoft Academic Search

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

1979-01-01

181

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

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

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

182

Wave Propagation over a Submarine Canyon: Field Observations  

NASA Astrophysics Data System (ADS)

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

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

2004-12-01

183

Radionuclide content of an exhumed canyon tank and neighboring soil  

Microsoft Academic Search

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

1977-01-01

184

Review of proposed Glen Canyon Dam interim operating criteria.  

National Technical Information Service (NTIS)

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

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

1992-01-01

185

Warm water interactions in the Barrow Canyon in winter  

NASA Astrophysics Data System (ADS)

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

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

1982-07-01

186

Mars  

NSDL National Science Digital Library

This NASA (National Aeronautics and Space Administration) planet profile provides data and images of the planet Mars. These data include planet size, orbit facts, distance from the Sun, rotation and revolution times, temperature, atmospheric composition, density, surface materials and albedo. Images with descriptions include surface features such as canyons, volcanoes, Viking 1 and 2 landing sites, the South Pole, plateaus, the Schiaparelli Crater, Amazonis Plains, Cerberus Crater, Valles Marineris, Chasma, Olympis Mons, and images of Mars two moons Phobos and Deimos. Images were taken by the Viking 1 and 2 Landers and the Viking Orbiter Spacecraft.

187

Mars Exploration Curriculum  

NSDL National Science Digital Library

This series of modules integrates printable images of Mars into classroom activities. Four broad topics cover the exploration of Mars and the Pathfinder missions, the great Martian floods and the Pathfinder landing site, the canyon Valles Marineris, and water on Mars. Each topic has several discrete activities associated with it that can be used independently. There are supporting materials for teachers as well as background information on the images. There are two curriculum modules for grades 4-10, one for grades 6-12 and one for grades 9-12.

188

Active geologic processes in Barrow Canyon, northeast Chukchi Sea  

USGS Publications Warehouse

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

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

1982-01-01

189

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

National Technical Information Service (NTIS)

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

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

1981-01-01

190

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

Microsoft Academic Search

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

Jochen Kämpf

2006-01-01

191

Channeling episodes of Kasei Valles, Mars, and the nature of ridged plains material  

Microsoft Academic Search

The geologic mapping compiled at 1:500,000 scale of the northern Kasei Valles area of Mars (MTMs 25062 and 25067) indicates (1) at least three periods of Kasei Valles channeling, (2) the development of Sacra Fossae (linear depressions on Tempe Terra and Lunae Planum) in relation to Kasei channeling episodes, and (3) the nature of ridged plains material dissected by Kasei

Mary G. Chapman; Kenneth L. Tanaka

1991-01-01

192

Experience the magic of light and color: outreach activity by Universidad del Valle student chapter  

Microsoft Academic Search

During 2007, the Universidad del Valle Student Chapter presented a proposal for developing an educational outreach activity for children from an underprivileged zone to the Optical Society of America Foundation (OSAF) and to SPIE. The activity was carried out jointly by OSA and SPIE Universidad del Valle Student Chapters in the hillsides of Santiago de Cali, in a zone known

Claudia Valdes; Camilo Reyes; Alberto Osorio; Efrain Solarte

2010-01-01

193

Shed Some Light on the Subject: Teaching Ramon del Valle-Inclan's "Luces de bohemia"  

ERIC Educational Resources Information Center

This essay seeks to provide parallel and interchangeable approaches to teaching Ramon del Valle-Inclan's challenging play "Luces de bohemia". A greater understanding of the cultural and mental frameworks of the early twentieth-century Spanish spectator will permit students to penetrate the dense intertextuality that characterizes Valle's…

Parker, Jason Thomas

2011-01-01

194

Channeling Episodes of Kasei Valles, Mars, and the Nature of Ridged Plains Material.  

National Technical Information Service (NTIS)

The geologic mapping compiled at 1:500,000 scale of the northern Kasei Valles area of Mars (MTMs 25062 and 25067) indicates (1) at least three periods of Kasei Valles channeling, (2) the development of Sacra Fossae (linear depressions on Tempe Terra and L...

M. G. Chapman K. L. Tanaka

1991-01-01

195

A Karst Connection model for Grand Canyon, Arizona, USA  

NASA Astrophysics Data System (ADS)

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

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

2008-03-01

196

Lynch Canyon combination thermal drive project. [Termination  

SciTech Connect

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

Stair, J. R.

1980-11-01

197

Report Summary, Final Hells Canyon Environmental Investigation.  

SciTech Connect

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

United States. Bonneville Power Administration.

1985-01-01

198

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

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

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

199

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

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

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

200

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

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

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

201

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

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

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

202

36 CFR 7.4 - Grand Canyon National Park.  

Code of Federal Regulations, 2013 CFR

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

2013-07-01

203

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

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

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

204

36 CFR 7.70 - Glen Canyon National Recreation Area.  

Code of Federal Regulations, 2013 CFR

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

2013-07-01

205

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

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

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

206

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

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

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

207

27 CFR 9.217 - Happy Canyon of Santa Barbara.  

Code of Federal Regulations, 2013 CFR

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

2013-04-01

208

Radionuclide Content of an Exhumed Canyon Tank and Neighboring Soil.  

National Technical Information Service (NTIS)

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

H. P. Holcomb

1977-01-01

209

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

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

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

210

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

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

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

211

H CANYON PROCESSING IN CORRELATION WITH FH ANALYTICAL LABS  

SciTech Connect

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

Weinheimer, E.

2012-08-06

212

Grand Canyon Glass Skywalk creates excitement and controversy  

NSDL National Science Digital Library

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

Grinnell, Max

213

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

Microsoft Academic Search

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

C. Rossen; J. F. Sarg

1987-01-01

214

Canyon dynamics and related sedimentary impacts off western Portugal  

NASA Astrophysics Data System (ADS)

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

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

2003-04-01

215

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

PubMed

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

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

2012-02-01

216

Submarine canyons: multiple causes and long-time persistence  

SciTech Connect

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

Shepard, F.P.

1981-06-01

217

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

USGS Publications Warehouse

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

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

2010-01-01

218

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

National Technical Information Service (NTIS)

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

A. A. Fox P. Ward

1986-01-01

219

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

Microsoft Academic Search

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

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

1980-01-01

220

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

Code of Federal Regulations, 2010 CFR

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

2010-01-01

221

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

Code of Federal Regulations, 2010 CFR

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

2009-01-01

222

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

Code of Federal Regulations, 2010 CFR

...Flight Rules in the Vicinity of the Grand Canyon National Park, AZ Appendix to...Flight Rules in the Vicinity of Grand Canyon National Park, AZ Pt. 93...Flight Rules in the Vicinity of the Grand Canyon National Park, AZ...

2009-01-01

223

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

Code of Federal Regulations, 2010 CFR

...Flight Rules in the Vicinity of the Grand Canyon National Park, AZ Appendix to...Flight Rules in the Vicinity of Grand Canyon National Park, AZ Pt. 93...Flight Rules in the Vicinity of the Grand Canyon National Park, AZ...

2010-01-01

224

76 FR 47237 - Notice of Public Meeting for the Glen Canyon Dam Adaptive Management Work Group Federal Advisory...  

Federal Register 2010, 2011, 2012, 2013

...Notice of Public Meeting for the Glen Canyon Dam Adaptive Management Work Group Federal Advisory...SUMMARY: The Glen Canyon Dam Adaptive Management Work Group (AMWG...Secretary of the Interior concerning Glen Canyon Dam operations and other management...

2011-08-04

225

Metamorphic signature of the Gneiss Canyon Shear Zone, Lower Granite Gorge, Grand Canyon, Arizona  

SciTech Connect

The Proterozoic orogen in Arizona consists of structural blocks separated by NE trending shear zones. The Gneiss Canyon Shear Zone (GCSZ) is important because it appears to define in part the boundary between the amphibolite facies Yavapai Province and the granulite facies Mojave Province. An early NW striking foliation is clearly visible in many samples from the Lower Granite Gorge (LGG). In Travertine Canyon, east of the GCSZ, pelitic schists contain And-Sil-Crd-Bi and Gar-Sil-Sta-Bi. Mafic rocks exhibit complex phase relations between cummingtonite, anthophyllite, gedrite, garnet, and cordierite. The coexistence of cordierite-cummingtonite is indicative of low pressure metamorphism. Microprobe analyses of garnets reveal prograde growth zoning profiles. Temperature and pressure estimates of peak metamorphism are 550--600 C and 3 kb. Just east of the GCSZ, pelitic assemblages contain Gar-Bi [+-] Sil [+-] Mus, and garnet zoning profiles are flat in the cores. In Spencer Canyon, west of the GCSZ, samples commonly contain Gar-Bi-Sil-Crd, and in many samples cordierite is being replaced by sillimanite. Thermobarometric calculations yield temperature and pressure estimates of 650 C and 3.5 kb. Mineral assemblages and quantitative thermobarometry suggest higher peak metamorphic temperature west of the GCSZ but relatively constant pressures across the LGG. On the east side of the GCSZ, temperatures increase toward the Shear Zone, probably due to the presence of extensive dikes, pods, and veins of variably deformed granite. Peak mineral assemblages are syntectonic with respect to the NE-striking GCSZ fabric. If a suture exists in the LGG, the GCSZ fabrics apparently reflect post-accretionary tectonism, with accretion occurring prior to the peak of metamorphism.

Robinson, K.; Williams, M.L. (Univ. of Massachusetts, Amherst, MA (United States). Dept. of Geology and Geography)

1992-01-01

226

Regional depositional history of the Miocene-Pleistocene Louisiana Slope, Green Canyon and Mississippi Canyon  

SciTech Connect

A regional sequence-stratigraphic analysis was recently completed for the Tertiary slope sediments in Green Canyon, Ewing Bank, and Mississippi Canyon to provide a chronostratigraphic framework for basin reconstructions and predict lithofacies distributions of reservoir and seal rocks. Sixteen third-order sequences of lowstand deep-water deposits were interpreted for the middle Miocene-Pleistocene section. Thirty regional lithofacies maps were made of predominantly lowstand deposits showing the distribution of shale and sand-prone sediments, slumping, channel levee systems, and fan lobes based on distinctive seismic reflection and well log patterns. These maps were combined with isochrons of selected sequences to identify depositional fairways, depocenters, and paleosalt positions that constantly changed through time. Depositional trends were principally north to south but were also observed to be east-west as salt modified the gradient on the gently dipping slope. In some cases, the structural and stratigraphic trends could be projected under allochthonous tabular salt. Miocene channel and fan lobe sands were found concentrated on the middle-lower paleoslope across the study area. The sedimentation rate doubled (0.7 m/1000 yr) in the early-middle Pliocene, which caused large-scale salt movements and trapped sand-prone turbidites along the upper-middle slope. A four-fold decrease in sediment influx during the late Pliocene-early Pleistocene produced a stacked condensed section of four sequences over the eastern Louisiana slope. A return to rapid sedimentation (up to 2.1 m/1000 yr.) during the Pleistocene reactivated salt movements and depocenters in the Green Canyon, Ewing Bank, and Mississippi Trough areas.

Risch, D.L.; Chowdhury, A.N.; Hannan, A.E. [Geco-Prakla, Houston, TX (United States)

1994-09-01

227

The bathypelagic community of Monterey Canyon  

NASA Astrophysics Data System (ADS)

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

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

2010-08-01

228

Investigation of Layered Sediments at a Proposed Future Landing Site in Ladon Valles  

NASA Astrophysics Data System (ADS)

We have identified candidate rover traverses and scientific targets within two proposed landing ellipses at the distal end of Ladon Valles. Both sites would enable potential access to sedimentary units of diverse morphologies and mineralogies.

Weitz, C. M.; Bishop, J. L.

2012-03-01

229

Downstream effects of Glen Canyon Dam on the Colorado River in Grand Canyon: A review  

NASA Astrophysics Data System (ADS)

Glen Canyon Dam, completed in 1963, has altered geomorphic and ecological processes and resources of the Colorado River in Grand Canyon. Before the dam was completed, the river transported large quantities of sediment during spring floods as large as 8500 m3/s. After 1963, dam releases typically were less than 900 m3/s with large diurnal fluctuations and little sediment. The 2-yr peak discharge decreased by a factor of 2.5, resulting in aggraded rapids and a large increase in riparian vegetation. The clearwater releases from the dam eroded sand deposited on the bed and banks. Although pre-dam water temperatures varied seasonally, dam releases typically are about 8°C year round. Because of the clear, cold water and reduced flooding, post-dam aquatic productivity is considerably higher in the tailwater. Rainbow trout and other non-native fishes are now common, 3 native species have been extirpated, and the remaining species, including the endangered humpback chub, cannot successfully reproduce in the river.

Webb, R. H.; Wegner, D. L.; Andrews, E. D.; Valdez, R. A.; Patten, D. T.

230

History and results of VC1, the first CSDP corehole in Valles caldera, New Mexico  

Microsoft Academic Search

Valles Caldera No. 1 (VC-1) is the first Continental Scientific Drilling Program (CSDP) corehole drilled in the Valles caldera and the first continuously cored hole in the caldera region. The objectives of VC-1 were to penetrate a hydrothermal outflow plume near its source, to obtain structural and stratigraphic information near the intersection of the ring-fracture zone and the pre-caldera Jemez

F. Goff; J. Rowley; J. N. Gardner; W. Hawkins; S. Goff; L. Pisto; G. Polk

1985-01-01

231

Organic geochemistry of submarine canyons: The Portuguese Margin  

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

232

BotEC: The Grand Canyon's Rate of Erosion  

NSDL National Science Digital Library

Question: Some geologic processes, like volcanism and earthquakes, occur intermittently but can cause significant and sometimes catastrophic change very quickly. Others, like weathering, act continuously but gradually, in fact, imperceptibly slow. Regardless of how they operate, geologic processes, acting over long periods of time (thousands and millions of years) will produce significant change in the earth's surface. If you were to occasionally visit the Grand Canyon over a period of many years, you would most likely notice no change. Even the details in the walls would probably seem frozen forever. Yet the Colorado River is continuously, albeit very slowly, cutting into and eroding the Colorado Plateau. The Grand Canyon is gradually being deepened and enlarged. Some geologists are finding evidence that suggests that this mile deep canyon may have been cut with the last 4 million years. Assuming a uniform rate of erosion and without considering canyon widening due to slop retreat, calculate how much (in millimeters per year) the Colorado River would have to downcut per year to form this mile-deep canyon in 4 million years.

Kresan, Peter

233

Software Configuration Management Plan for the B-Plant Canyon Ventilation Control System  

SciTech Connect

Project W-059 installed a new B Plant Canyon Ventilation System. Monitoring and control of the system is implemented by the Canyon Ventilation Control System (CVCS). This Software Configuration Management Plan provides instructions for change control of the CVCS.

MCDANIEL, K.S.

1999-08-31

234

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

Code of Federal Regulations, 2010 CFR

...Canyon Nuclear Power Plant, Avila Beach...Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF HOMELAND SECURITY...Canyon Nuclear Power Plant, Avila Beach...security zone: all waters of the Pacific...the Port, Los Angeles-Long...

2010-07-01

235

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

Code of Federal Regulations, 2013 CFR

...Canyon Nuclear Power Plant, Avila Beach...Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF HOMELAND SECURITY...Canyon Nuclear Power Plant, Avila Beach...security zone: all waters of the Pacific...the Port, Los Angeles-Long...

2013-07-01

236

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

Code of Federal Regulations, 2010 CFR

...Canyon Nuclear Power Plant, Avila Beach...Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF HOMELAND SECURITY...Canyon Nuclear Power Plant, Avila Beach...security zone: all waters of the Pacific...the Port, Los Angeles-Long...

2009-07-01

237

75 FR 76650 - Proposed Modification of Class E Airspace; Bryce Canyon, UT  

Federal Register 2010, 2011, 2012, 2013

...accommodate Area Navigation (RNAV) Global Positioning System (GPS) Standard Instrument Approach Procedures at Bryce Canyon Airport...airspace is necessary to accommodate aircraft using the RNAV (GPS) Standard Instrument Approach Procedures at Bryce Canyon...

2010-12-09

238

75 FR 39147 - Establishment of Class E Airspace; Bryce Canyon, UT  

Federal Register 2010, 2011, 2012, 2013

...establish Class E airspace at Bryce Canyon, UT, to accommodate aircraft using a new Area Navigation (RNAV) Global Positioning System (GPS) Standard Instrument Approach Procedures (SIAPs) at Bryce Canyon Airport. This will improve the...

2010-07-08

239

Tar Sand Occurrences in the Bush Butte Quadrangle, Wyoming, with Emphasis on the Trapper Canyon Deposit.  

National Technical Information Service (NTIS)

The Trapper Canyon Tar Sand Deposit is located in the eastern Bighorn Basin, approximately 25 miles east of Greybull, Wyoming. This project not only involved detailed geologic mapping of the Trapper Canyon Tar Sand Deposit, but also sampling and describin...

A. J. VerPloeg R. H. DeBruin

1983-01-01

240

Live (stained) benthic foraminifera from the Cap-Ferret Canyon (Bay of Biscay, NE Atlantic): A comparison between the canyon axis and the surrounding areas  

NASA Astrophysics Data System (ADS)

Living (Rose Bengal stained) benthic foraminiferal faunas were investigated at 13 deep-sea stations sampled in the Cap-Ferret Canyon area (NE Atlantic). One station (151 m) is located on the continental shelf close to the canyon head. All other stations are located along 2 bathymetric transects: 7 sites along the canyon axis with depths ranging from 300 to 3000 m and 5 stations along the adjacent flank with depths ranging from 300 m to 2000 m. Sedimentological analyses indicate that the Cap-Ferret Canyon is at present inactive in terms of sediment gravity flow. Compared to stations on the adjacent flank, canyon-axis stations are generally characterised by shallow oxygen penetration depths, high diffusive oxygen uptakes (DOU) and high lipid contents. Higher mineralisation rates recorded in the canyon axis are likely due to a preferential focusing of labile organic matter in the canyon axis. Foraminiferal standing stocks do not exhibit any straightforward correlation with the different descriptors of organic matter available in the sediment. However, foraminiferal standing stock and diversity along the canyon axis are generally higher than on the adjacent flank. Canyon axis sites yield dominant species that are similar to those at adjacent flank and open slope stations located at comparable water depths. However, intermediate and deep infaunal species were only recorded in the lower canyon axis, where high amounts of organic matter were observed in deeper sediment layers. Finally, the faunal composition in the Cap-Ferret Canyon is different compared to the nearby Cap-Breton Canyon, where sediment gravity flows are active. The absence of pioneer species and the occurrence of highly specialized taxa are both consistent with the much more stable conditions in terms of hydro-sedimentary conditions prevailing in the Cap-Ferret Canyon.

Duros, P.; Fontanier, C.; Metzger, E.; Cesbron, F.; Deflandre, B.; Schmidt, S.; Buscail, R.; Zaragosi, S.; Kerhervé, P.; Rigaud, S.; Delgard, M.-L.; Jorissen, F. J.

2013-04-01

241

patterns of dust transport to the Grand Canyon  

NASA Astrophysics Data System (ADS)

Dust particles in the 2.5 µm to 15 µm diameter range contribute to regional haze that sometimes impairs visibility at the Grand Canyon and other National Parks in the southwestern U.S. The proportion of airborne dust that is attributable to land modification is unknown, but can be expected to increase as a consequence of the region's rapid population growth. This note examines the upwind histories of air masses bringing high coarse-particle concentrations to the Grand Canyon over a five-year monitoring period. Although arid and semi-arid lands extend in all directions, and the fastest airflows generally have a northerly component, high dust concentrations are most common in air arriving from the southwest, where development has been concentrated. This empirical association suggests that the expansion of suburban and agricultural lands is raising dust levels at the Grand Canyon.

de P. Vasconcelos, Luis A.; Kahl, Jonathan D. W.; Liu, Desong; Macias, Edward S.; White, Warren H.

242

Scattering of SH waves by a circular sectorial canyon  

NASA Astrophysics Data System (ADS)

The scattering of plane SH waves incident on a circular sectorial canyon is considered. An accurate region-matching technique is applied to derive a rigorous series solution. Appropriate wavefunctions are employed to describe antiplane motions. Judicious basis functions, involving Gegenbauer polynomials, are well utilized to correctly capture the singular behaviour in stress fields near the canyon bottom. The enforcement of matching conditions on the auxiliary boundary leads to the determination of unknown coefficients. Plotted results demonstrate the influence of pertinent parameters on surface and subsurface motions. Both steady-state and transient results are included. The solution technique proposed achieves a considerable reduction in the computational effort, facilitating benchmark computations. The derived series solution enriches the limited list of series solutions presently known for canyon problems related to SH-wave scattering.

Chang, Kao-Hao; Tsaur, Deng-How; Wang, Jeen-Hwa

2013-10-01

243

78 FR 42902 - Safety Zone; Olympus Tension Leg Platform, Mississippi Canyon Block 807, Outer Continental Shelf...  

Federal Register 2010, 2011, 2012, 2013

...Olympus Tension Leg Platform, Mississippi Canyon Block 807, Outer Continental Shelf...the Olympus Tension Leg Platform, Mississippi Canyon Block 807 on the [[Page 42903...deepwater area of the Gulf of Mexico in Mississippi Canyon Block 807B. The facility is...

2013-07-18

244

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

Microsoft Academic Search

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

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

2004-01-01

245

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

Microsoft Academic Search

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

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

1999-01-01

246

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

247

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

248

A wind tunnel study of organised and turbulent air motions in urban street canyons  

Microsoft Academic Search

High concentrations of car-exhaust gases in urban street canyons are typically associated with low wind velocities or situations when the wind blows perpendicular to the canyon axis. The latter flow configuration has been studied in a wind tunnel model of a street canyon. The mean flow and turbulence structure have both been investigated and comparisons have been carried out with

P. Kastner-Klein; E. Fedorovich; M. W. Rotach

2001-01-01

249

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

Microsoft Academic Search

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

S. O. Olabode; J. A. Adekoya

2008-01-01

250

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

Microsoft Academic Search

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

Peter T. Harris; Tanya Whiteway

2011-01-01

251

76 FR 54487 - Charter Renewal, Glen Canyon Dam Adaptive Management Work Group  

Federal Register 2010, 2011, 2012, 2013

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

2011-09-01

252

78 FR 42799 - Glen Canyon Dam Adaptive Management Work Group Meetings  

Federal Register 2010, 2011, 2012, 2013

...X30-0594-0913-700-00-0-0, 4073000] Glen Canyon Dam Adaptive Management Work Group Meetings...SUMMARY: The Glen Canyon Dam Adaptive Management Work Group (AMWG...Secretary of the Interior concerning Glen Canyon Dam operations and other management...

2013-07-17

253

Temperature decreases in an urban canyon due to green walls and green roofs in diverse climates  

Microsoft Academic Search

This paper discusses the thermal effect of covering the building envelope with vegetation on the microclimate in the built environment, for various climates and urban canyon geometries. A two-dimensional, prognostic, micro scale model has been used, developed for the purposes of this study. The climatic characteristics of nine cities, three urban canyon geometries, two canyon orientations and two wind directions

Eleftheria Alexandri; Phil Jones

2008-01-01

254

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

Microsoft Academic Search

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

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

2005-01-01

255

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

Microsoft Academic Search

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

Adam Klaus; Brian Taylor

1991-01-01

256

On the magnitude of upwelling fluxes in shelf-break canyons  

NASA Astrophysics Data System (ADS)

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

Kämpf, Jochen

2007-10-01

257

Thirty-five years at Pajarito Canyon Site  

SciTech Connect

A history of the research activities performed at the Pajarito Canyon Site from 1946 to 1981 is presented. Critical assemblies described include: the Topsy assembly; Lady Godiva; Godiva 2; Jezebel; Flattop; the Honeycomb assembly for Rover studies; Kiwi-TNT; PARKA reactor; Big Ten; and Plasma Cavity Assembly.

Paxton, H.C.

1981-05-01

258

Anomalous topography on the continental shelf around Hudson Canyon  

USGS Publications Warehouse

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

Knebel, H. J.

1979-01-01

259

Proposed Black Canyon of the Gunnison National Monument, Colorado.  

National Technical Information Service (NTIS)

The National Park Service proposes a plan for the establishment and management of an 8,780-acre wilderness area. The area, which is about 64% of the monument's acreage, embraces all of the canyon and a portion of the mesa and bench land. Environmental imp...

1973-01-01

260

A modeling of air flow in a street canyon  

NASA Astrophysics Data System (ADS)

Steady plane-parallel isothermal turbulent flow of a viscous incompressible liquid above a surface with elements of a roughness is considered. Buildings and road with vehicle emissions for a city canyon. Reynolds equations and Boussinesq assumption are used to solve the considered problem. We apply the no-slip boundary conditions on the rigid walls, simple gradient conditions on the upper and outflow boundaries and known distributions of flow parameters on inflow boundary. Turbulent parameters are calculated on the basis of "k--?" model of turbulence with near-wall functions approach for energy of turbulence k and dissipation ?. A numerical solution of the problem is found with using of finite-volume method and the SIMPLE algorithm. Influence of atmospheric parameters on pollutant dispersion in a street canyon is investigated. Also influences of the geometrical factors of a city street canyon on a pattern of turbulent flow and distribution of harmful impurity concentration emitting from urban vehicles are investigated. The adverse meteorological situations resulting in accumulation of the harmful substances in street canyon are shown.

Nuterman, R. B.; Starchenko, Alexander V.

2004-02-01

261

National Uranium Resource Evaluation, Grand Canyon Quadrangle, Arizona  

Microsoft Academic Search

The Grand Canyon Quadrangle (2°), northwestern Arizona, was evaluated to identify environments and delineate areas favorable for the occurrence of uranium deposits. This was done using criteria developed for the National Uranium Resource Evaluation. General surface reconnaissance and geochemical sampling were carried out in all geologic environments within the quadrangle. Aerial radiometric and hydrochemical and stream-sediment reconnaissance surveys were performed,

T. A. Baillieul; R. C. Zollinger

1982-01-01

262

College of the Canyons Syllabus Survey, Spring 2002. Report.  

ERIC Educational Resources Information Center

This study was conducted at College of the Canyons (COC), California, in spring 2002 by the Office of Institutional Development and Technology, along with Communications Studies instructor Victoria Leonard. Eighty-three class sections were surveyed to determine the degree to which students agreed or disagreed that their course syllabus clearly…

Meuschke, Daylene M.; Gribbons, Barry C.; Dixon, Scott P.

263

College of the Canyons New Faculty Survey. Report #104.  

ERIC Educational Resources Information Center

In 2001, the College of the Canyons (COC) (California) surveyed all faculty members hired between May 2000 and March 2001 to gather information about the experiences of newly hired faculty. Thirty-eight anonymous questionnaires (with both open- and closed-ended questions) were placed in the mailboxes of new faculty; 23 were completed and returned,…

Dixon, P. Scott; Gribbons, Barry C.

264

Modelling air quality in street canyons: a review  

Microsoft Academic Search

High pollution levels have been often observed in urban street canyons due to the increased traffic emissions and reduced natural ventilation. Microscale dispersion models with different levels of complexity may be used to assess urban air quality and support decision-making for pollution control strategies and traffic planning. Mathematical models calculate pollutant concentrations by solving either analytically a simplified set of

Sotiris Vardoulakis; Bernard E. A Fisher; Koulis Pericleous; Norbert Gonzalez-Flesca

2003-01-01

265

9. COULTERVILLE ROAD VIEW AND MERCED RIVER CANYON. NOTE CUT ...  

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

9. COULTERVILLE ROAD VIEW AND MERCED RIVER CANYON. NOTE CUT FACE OF STANDING ROCK AT RIGHT. LOOKING N. GIS: N-37 42 52.1 / W-119 43 17.5 - Coulterville Road, Between Foresta & All-Weather Highway, Yosemite Village, Mariposa County, CA

266

56. ASSEMBLY OF THE VAL BRIDGE STRUCTURE AT ISLIP CANYON, ...  

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

56. ASSEMBLY OF THE VAL BRIDGE STRUCTURE AT ISLIP CANYON, July 31, 1947. (Original photograph in possession of Dave Willis, San Diego, California.) - Variable Angle Launcher Complex, Variable Angle Launcher, CA State Highway 39 at Morris Reservior, Azusa, Los Angeles County, CA

267

Novel observations on the massive Barkley Canyon hydrates  

Microsoft Academic Search

We report on the early results of an August 2006 expedition to the massive exposed hydrates found at 850m depth in Barkley Canyon, off-shore Vancouver Island. We used the ROV Tiburon to explore, image, and sample the site, and also to carry out a series of novel experimental techniques and measurements in situ. We used the DORISS II laser Raman

P. G. Brewer; E. T. Peltzer; W. J. Kirkwood; R. M. Dunk; P. Walz; K. Hester; E. D. Sloan

2006-01-01

268

Seismic stratigraphy of northern Green Canyon area, Gulf of Mexico  

Microsoft Academic Search

The Green Canyon area of the Gulf of Mexico is an active frontier exploration area of the continental slope underlain by relatively shallow salt or shale diapirs and ridges forming large intraslope basins and troughs. Analysis of more than 200 multichannel seismic profiles in this area show several seismic sequences within each basin or trough. The depositional history of the

R. G. Mann; W. R. Bryant

1986-01-01

269

Crisscrossing "Grand Canyon": Bridging the Gaps with Computer Conferencing.  

ERIC Educational Resources Information Center

Notes that Interdisciplinary Studies Program faculty at Wayne State University devised courses and assignments using computer conferencing to create a collaborative, democratic, and nonauthoritarian learning community. Discusses an assignment based on the film "Grand Canyon" that encouraged students to take on roles of their racial and gender…

Minock, Mary; Shor, Francis

1995-01-01

270

When did the Grand Canyon Begin to Form?  

NSDL National Science Digital Library

This post, originally published in the Connecting News with National Science Education Standards blog, deals with the findings suggesting the Grand Canyon is two to three times older than commonly believed. Ideas for engaging students in a thoughtful discussion about these research findings are provided.

Lefever, Mary; Hamilton, Carolyn

2008-03-14

271

Litter in submarine canyons off the west coast of Portugal  

Microsoft Academic Search

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

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

2011-01-01

272

Grand Canyon Trekkers: School-Based Lunchtime Walking Program  

ERIC Educational Resources Information Center

|The incidence of childhood overweight is especially troubling among low income Latino youth. Grand Canyon Trekkers (GCT) was implemented as a quasi-experimental study in 10 Title 1 elementary schools with a large Latino population to examine the effects of a 16-week structured walking program on components of health-related physical fitness: Body…

Hawthorne, Alisa; Shaibi, Gabriel; Gance-Cleveland, Bonnie; McFall, Sarah

2011-01-01

273

Geology Fieldnotes: Black Canyon of the Gunnison National Park, Colorado  

NSDL National Science Digital Library

Geologic information on this site includes details about how the Black Canyon was formed by the Gunnison river, metamorphic rock types, wildlife, archeology, and early exploration of the area. Also provided are links to visitor information, multimedia resources, park maps, and photographs.

274

Properties of Saltstone Prepared Containing H-Canyon Waste  

SciTech Connect

Saltstone slurries were prepared from solutions made from H-Canyon waste and evaluated for processing properties. Salt solutions prepared with a 1:1 ratio of Tank 50H simulant and H-Canyon blended waste produced slurries that met the processing requirements in Table 2 of the Task Technical and Quality Assurance Plan (TTQAP). Additions of set retarder and antifoam were necessary to meet these processing requirements. The water to premix ratio used to achieve acceptable processing properties was 0.63. Slurries prepared solely with H-Canyon blended waste as the salt solution met the gel time and bleed water requirements, but did not set in the allotted time. Compressive strength samples prepared from the mix with acceptable processing properties had an average compressive strength of 814 psi (Samples with a compressive strength value of >200 psi are acceptable.). Analysis for mercury of the leachate of samples analyzed by the Toxic Characteristic Leaching Procedure (TCLP) indicated a concentration of mercury in the leachate <0.11 mg/L (The limit set by the Environmental Protection Agency (EPA) Resource Conservation and Recovery Act (RCRA) for mercury to require treatment is 0.2 mg/L.). It is recommended that without further testing; Tank 50H be limited to no more than 50 wt% H-Canyon material. It is also recommended that prior to the transfer of Tank 50H to the Saltstone Processing Facility; a sample of the Tank 50H waste be evaluated for processing properties.

Cozzi, A

2005-04-05

275

Final Environmental Impact Statement. Grapevine Canyon Wind Project. Volume 1.  

National Technical Information Service (NTIS)

The Grapevine Canyon Wind Project proposed by Foresight Flying M, LLC (Foresight) would include: (1) a wind energy generating facility up to 500 megawatts; (2) a 345-kilovolt (kV) electrical transmission tie-line; and (3) a 345-kV electrical interconnecti...

2012-01-01

276

When less is less: Waste minimization at Diablo Canyon  

SciTech Connect

At Diablo Canyon power plant, Pacific Gas and Electric has implemented a minimization plan to reduce the generation of radioactive waste. The plan encompasses wastes generated from plant systems, from the modification of plant systems and structures, and from the use of protective clothing and contamination control consumables.

Miller, C.C. [Pacific Gas & Electric Company, Avila Beach, CA (United States)

1995-12-31

277

The Grand Canyon of the Yellowstone by Lucien Powell  

USGS Multimedia Gallery

This large (74" X 114.5") oil painting was done by Lucien W. Powell and is on loan to the Geological Survey from the Smithsonian National Museum of American Art. The title of the painting is The Grand Canyon of the Yellowstone. Object ID: USGS-575066...

2009-07-22

278

Carbonaceous aerosol particles from common vegetation in the Grand Canyon  

SciTech Connect

The problem of visibility reduction in the Grand Canyon due to fine organic aerosol particles in the atmosphere has become an area of increased environmental concern. Aerosol particles can be derived from many emission sources. In this report, we focus on identifying organic aerosols derived from common vegetation in the Grand Canyon. These aerosols are expected to be significant contributors to the total atmospheric organic aerosol content. Aerosol samples from living vegetation were collected by resuspension of surface wax and resin components liberated from the leaves of vegetation common to areas of the Grand Canyon. The samples were analyzed using high-resolution gas chromatography/mass spectrometry (GC/MS). Probable identification of compounds was made by comparison of sample spectra with National Institute of Standards and Technology (NIST) mass spectral references and positive identification of compounds was made when possible by comparison with authentic standards as well as NIST references. Using these references, we have been able to positively identify the presence of n-alkane and n-alkanoic acid homolog series in the surface waxes of the vegetation sampled. Several monoterpenes, sesquiterpenes, and diterpenes were identified also as possible biogenic aerosols which may contribute to the total organic aerosol abundance leading to visibility reduction in the Grand Canyon.

Hallock, K.A.; Mazurek, M.A. (Brookhaven National Lab., Upton, NY (United States)); Cass, G.R. (California Inst. of Tech., Pasadena, CA (United States). Dept. of Environmental Engineering Science)

1992-05-01

279

Scientific core hole VC-2A, Valles Caldera, New Mexico  

SciTech Connect

This report details the remedial action activities that were necessary to complete scientific core hole Valles caldera {number sign}2A (VC-2A) before it was relinquished to the landowners. Sandia National Laboratories, acting as the Geoscience Research Drilling Office (GRDO), managed the coring operations. Los Alamos National Laboratory (Los Alamos) obtained the proper drilling permits with the New Mexico State Engineers Office (SEO). A legal agreement between Los Alamos and the landowners states that the Laboratory will give the landowners the completed core hold with casing, well head, and other hardware at the end of May 1991, or earlier if scientific investigations were completed. By May 1988, the Science Team completed the planned scientific investigations in the VC-2A core hole. Upon the insistence of the GRDO, the New Mexico Oil Conservation Division (OCD) inspected the core hole, declared jurisdiction, and required that the 11.43- by 11.43-cm annular cement job be repaired to comply with OCD regulations. These regulations state that there must be a return to surface of cement in all cementing operations. We successfully completed a squeeze cementing operation and relinquished the core hold to the landowners in November 1988 to the satisfaction of the OCD, SEO, the landowners, and Los Alamos. 7 refs., 4 figs., 1 tab.

Musgrave, J.; Goff, S. (Los Alamos National Lab., NM (USA)); Turner, T. (Turner (Tom), Salt Lake City, UT (USA))

1990-10-01

280

Cosmogenic 3He ages and frequency of late Holocene debris flows from Prospect Canyon, Grand Canyon, USA  

USGS Publications Warehouse

Lava Falls Rapid, which was created and is maintained by debris flows from Prospect Canyon, is the most formidable reach of whitewater on the Colorado River in Grand Canyon and is one of the most famous rapids in the world. Debris flows enter the Colorado River at tributary junctures, creating rapids. The frequency of debris flows is an important consideration when management of regulated rivers involves maintenance of channel morphology. We used cosmogenic 3He, 14C, and historical photographs to date 12 late Holocene and historic debris flows from Prospect Canyon. The highest and oldest deposits from debris flows on the debris fan yielded a 3He date of about 3 ka, which indicates predominately late Holocene aggradation of one of the largest debris fans in Grand Canyon. The deposit, which has a 25-m escarpment caused by river reworking, crossed the Colorado River and raised its base level by 30 m for an indeterminate although likely short period. We mapped depositional surfaces of 11 debris flows that occurred after 3 ka. Two deposits inset against the highest deposit yielded 3He ages of about 2.2 ka, and at least two others followed shortly afterwards. At least one of these debris flows also dammed the Colorado River. The most recent prehistoric debris flow occurred no more than 0.5 ka. The largest historic debris flow, which constricted the river by 80%, occurred in 1939. Five other debris flows occurred after 1939; these debris flows constricted the Colorado River by 35-80%. Assuming the depositional volumes of late Holocene debris flows can be modeled using a lognormal distribution, we calculated recurrence intervals of 15 to more than 2000 years for debris flows from Prospect Canyon.

Cerling, T. E.; Webb, R. H.; Poreda, R. J.; Rigby, A. D.; Melis, T. S.

1999-01-01

281

Field trip guide to the Valles Caldera and its geothermal systems  

SciTech Connect

This field trip guide has been compiled from extensive field trips led at Los Alamos National Laboratory during the past six years. The original version of this guide was designed to augment a workshop on the Valles Caldera for the Continental Scientific Drilling Program (CSDP). This workshop was held at Los Alamos, New Mexico, 5-7 October 1982. More stops were added to this guide to display the volcanic and geothermal features at the Valles Caldera. The trip covers about 90 miles (one way) and takes two days to complete; however, those who wish to compress the trip into one day are advised to use the designated stops listed in the Introduction. Valles Caldera and vicinity comprise both one of the most exciting geothermal areas in the United States and one of the best preserved Quaternary caldera complexes in the world.

Goff, F.E.; Bolivar, S.L.

1983-12-01

282

New observations of Warrego Valles, Mars: Evidence for precipitation and surface runoff  

NASA Astrophysics Data System (ADS)

Most valley networks have been identified primarily in the heavily cratered uplands which are Noachian in age (>3.5 Gyr). A striking exception to this general observation is Warrego Valles located on the southeastern part of the Tharsis bulge. Recent data obtained by the Mars Orbiter Laser Altimeter, the Thermal Emission Imaging System (THEMIS) spectrometer and the Mars Orbiter Camera give new insight into the formation of valley networks and the early Mars climate. We focus our study on the southern Thaumasia region especially on Warrego Valles and determine the organisation of valleys in relation to regional topography and structural geology. Warrego Valles is the most mature valley network that incised the southern side of Thaumasia highlands. It developed in a rectangular-shaped, concave-up drainage basin. Four times more valleys are identified in THEMIS infrared images than in Viking images. Valleys exist on both sides of the main tributary contrary to what was visible in Viking images. Their distribution is highly controlled by topographic slope, e.g. there is a parallel pattern on the sides and dendritic pattern on the central part of Warrego Valles. We quantitatively analyse valley morphology and morphometry to determine the processes responsible for valley network formation. Warrego Valles displays morphometric properties similar to those of a terrestrial fluvial valley network. This valley network is characterised by seven Strahler's orders, a bifurcation ratio of 3, a length ratio of 1.7, a drainage density of 0.53 km-1 and a ruggedness number of 3.3. The hypsometric curve and integral (0.46) indicate that Warrego Valles reached the mature Davis’ stage. Valleys have undergone external degradation since their incision, which masks their main morphological characteristics. Our study supports the assertion that valley networks formed by fluvial processes controlled by an atmospheric water cycle. Further, they seem to develop by successive stages of erosion that occurred during Noachian through the late Hesperian.

Ansan, V.; Mangold, N.

2006-03-01

283

Environmental analysis of Lower Pueblo/Lower Los Alamos Canyon, Los Alamos, New Mexico  

SciTech Connect

The radiological survey of the former radioactive waste treatment plant site (TA-45), Acid Canyon, Pueblo Canyon, and Los Alamos Canyon found residual contamination at the site itself and in the channel and banks of Acid, Pueblo, and lower Los Alamos Canyons all the way to the Rio Grande. The largest reservoir of residual radioactivity is in lower Pueblo Canyon, which is on DOE property. However, residual radioactivity does not exceed proposed cleanup criteria in either lower Pueblo or lower Los Alamos Canyons. The three alternatives proposed are (1) to take no action, (2) to construct a sediment trap in lower Pueblo Canyon to prevent further transport of residual radioactivity onto San Ildefonso Indian Pueblo land, and (3) to clean the residual radioactivity from the canyon system. Alternative 2, to cleanup the canyon system, is rejected as a viable alternative. Thousands of truckloads of sediment would have to be removed and disposed of, and this effort is unwarranted by the low levels of contamination present. Residual radioactivity levels, under either present conditions or projected future conditions, will not result in significant radiation doses to persons exposed. Modeling efforts show that future transport activity will not result in any residual radioactivity concentrations higher than those already existing. Thus, although construction of a sediment trap in lower Pueblo Canyon is a viable alternative, this effort also is unwarranted, and the no-action alternative is the preferred alternative.

Ferenbaugh, R.W.; Buhl, T.E.; Stoker, A.K.; Becker, N.M.; Rodgers, J.C.; Hansen, W.R.

1994-12-01

284

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

285

Restoring Anadromous Fish Habitat in Big Canyon Creek Watershed; Anadromous Fish Habitat Restoration in the Nichols Canyon Subwatershed, 1999 Annual Report.  

SciTech Connect

Nez Perce Soil & Water Conservation District (NPSWCD) undertook the Nichols Canyon Subwatershed Steelhead Trout Habitat Improvement Project in the spring of 1999. This Project is funded through a grant provided by the Bonneville Power Administration. The Project's purpose is to install and implement agricultural best management practices (BMPs) and riparian restorations to improve steelhead trout spawning and rearing habitat in the Nichols Canyon subwatershed of Big Canyon Creek. Improvements to spawning and rearing habitat in lower Big Canyon Creek tributaries will enhance natural production of the species in Big Canyon Creek and ultimately the Clearwater River. The following report is a summation of the activities undertaken by the NPSWCD in the first year of the project.

Koziol, Deb (Nez Perce Soil and Water Conservation District, Lewiston, ID)

2000-02-01

286

Cyclone-induced hyperpycnal turbidity currents in a submarine canyon  

NASA Astrophysics Data System (ADS)

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

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

2012-04-01

287

Rapid export of organic matter to the Mississippi Canyon  

NASA Astrophysics Data System (ADS)

Coastal margins, where rivers serve as the dominant control on productivity and delivery of dissolved and particulate materials, have been understudied.The potential importance of certain river-dominated margins (RiOMars), such as those of the Mississippi River plume, to the global carbon budget is garnering increased attention because of their disproportionate role in transporting terrigenous materials to the ocean [Dagg et al., 2004; McKee et al., 2004].This study concludes that labile (readily open to chemical, physical, or biological change) sedimentary organic matter, produced by in situ diatom production in the Mississippi River plume, is rapidly transported to the Mississippi Canyon. Despite the notion that canyon sediments are typically unstable and lack adequate food resources to support significant macrobenthic communities, this study suggests that productive RiOMars are important conduits for transporting fixed carbon from highly productive plume waters on the shelf to deeper benthic communities.

Bianchi, Thomas S.; Allison, Mead A.; Canuel, Elizabeth A.; Reide Corbett, D.; McKee, Brent A.; Sampere, Troy P.; Wakeham, Stuart G.; Waterson, Elizabeth

2006-12-01

288

Paleofluvial mega-canyon beneath the central Greenland ice sheet.  

PubMed

Subglacial topography plays an important role in modulating the distribution and flow of basal water. Where topography predates ice sheet inception, it can also reveal insights into former tectonic and geomorphological processes. Although such associations are known in Antarctica, little consideration has been given to them in Greenland, partly because much of the ice sheet bed is thought to be relatively flat and smooth. Here, we present evidence from ice-penetrating radar data for a 750-km-long subglacial canyon in northern Greenland that is likely to have influenced basal water flow from the ice sheet interior to the margin. We suggest that the mega-canyon predates ice sheet inception and will have influenced basal hydrology in Greenland over past glacial cycles. PMID:23990558

Bamber, Jonathan L; Siegert, Martin J; Griggs, Jennifer A; Marshall, Shawn J; Spada, Giorgio

2013-08-30

289

Hydraulics of outburst floods spilling over a steep-walled canyon: Implications for paleo-discharges on Mars  

NASA Astrophysics Data System (ADS)

Canyons carved by outburst floods are common landforms on Earth and Mars. These canyons are generally found in fractured basalts and jointed sedimentary rocks. Flood-carved canyons commonly have steep headwalls and a roughly constant width, and are often thought to have formed from upstream headwall propagation due to waterfall erosion. Because morphology is readily available from satellite imagery, these canyons offer a unique opportunity to quantify the discharge of rare, catastrophic paleo-floods on Earth and Mars. However, mechanistic relationships that relate canyon size to flood discharge have yet to be developed. We propose that the width of a canyon headwall in fractured rock is set by the spatial distribution of erosion around the rim of the canyon, which is controlled by the distribution of shear stresses induced by the overflowing water as it is focused into the canyon head. We test this hypothesis by performing a series of numerical simulations of flood-water focusing using ANUGA Hydro, a 2D-depth averaged, fully turbulent, hydraulic numerical modeling suite allowing for Froude-number transitions. The numerical simulations were designed to explore five dimensionless variables: the aspect ratio of the canyon (length normalized by width), the canyon width to flood-water width ratio, the canyon width to normal-flow depth ratio, the Froude number, and the topographic gradient upstream of the canyon. Preliminary results show that flow focusing leads to increased shear stresses at the canyon head compared to the sides of the canyon for subcritical floods and higher canyon aspect ratios. This suggests that proto-canyons start growing from a topographic defect in all directions until they reach a critical length for the side walls to dry. Once this critical length is attained, canyons focus most of the flood waters into their heads, and propagate upstream only, maintaining roughly constant widths. Preliminary results suggest that canyon width may be used to reconstruct the discharge of paleo-flood events on Mars and Earth.

Lapotre, Mathieu; Lamb, Michael

2013-04-01

290

The role of radiative-convective interaction in creating the microclimate of urban street canyons  

NASA Astrophysics Data System (ADS)

An approximate sky view factor (SVF) has been developed, which is capable of estimating the mean rate of net longwave radiant energy loss from urban street canyons. Reduced scale models of typical canyon geometries were used in outdoor tests to verify the predictions of radiant fluxes obtained using the proposed SVF. Air-surface temperature differences from the scale models are used together with hypothesized within-canyon airflow patterns to determine some quantitative characteristics of the wind field in canyons. Simple correlations are proposed for the relationship between mean in-canyon and pedestrian-level flow speeds on the one hand, and the ambient (above roof-level) wind speed on the other hand. As expected, the height/width ratio of a canyon controls the form and magnitude of the flow within.

Swaid, Hanna

1993-04-01

291

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

NASA Astrophysics Data System (ADS)

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

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

2013-01-01

292

Incision History of the Black Canyon of the Gunnison  

Microsoft Academic Search

The Gunnison River is the major tributary of the Colorado River that drains some of the highest topography of the Colorado Rocky Mountains. Paleo river profiles at 640ka, 10Ma, and ~35Ma provide benchmarks to understand the long-term incision history of the Black Canyon. Reconstruction of these paleo profiles is based on elevated bedrock straths and alluvial deposits that can be

M. Sandoval; K. E. Karlstrom; A. Aslan; E. Kirby; D. Granger

2006-01-01

293

Environmental geochemistry of the Bingham Canyon porphyry copper deposit, Utah  

Microsoft Academic Search

At the Bingham Canyon porphyry copper deposit, sulfide mineralization progresses outward from a low-grade core through the following general zones: (1) molybdenite, (2) chalcopyrite-bornite, (3) chalcopyrite-pyrite, (4) pyrite, and (5) sphalerite-galena. The low-grade core and the molybdenite zone are composed of net neutralizing rock and will generally not acidify when exposed to surface weathering conditions. The copper-bearing zones of the

Richard K. Borden

2003-01-01

294

Distribution of indicator bacteria in Canyon Lake, California  

Microsoft Academic Search

The spatial and temporal distributions of indicator bacteria in a small, multiple-use source drinking water reservoir in Southern California, USA were quantified over the period August 2001–July 2002. High levels of total and fecal coliform bacteria were present in Canyon Lake (annual geometric mean concentrations±SEM of 3.93±0.02 and 3.02±0.03logcfu\\/100mL, respectively), while comparatively low levels of enterococci and E. coli were

Kristal Davis; Michael A. Anderson; Marylynn V. Yates

2005-01-01

295

Grand Canyon Exercise: Geological Time, History, and Sedimentary Environments.  

NSDL National Science Digital Library

This site presents a take-home web-based project for introductory geology students. The exercise has the students interpreting the sedimentary geology (lithology and fossils) of the Grand Canyon to create a geological history for the region. It is an open-ended exercise with no absolutely correct answer; it involves students acting as scientists - that is, the way real scientists think and combine information to come up with explanations.

Perkins, Dexter

1998-01-01

296

The Dissolution of Desicooler Residues in H-Canyon Dissolvers  

SciTech Connect

A series of dissolution and characterization studies has been performed to determine if FB-Line residues stored in desicooler containers will dissolve using a modified H-Canyon processing flowsheet. Samples of desicooler materials were used to evaluate dissolving characteristics in the low-molar nitric acid solutions used in H-Canyon dissolvers. The selection for the H-Canyon dissolution of desicooler residues was based on their high-enriched uranium content and trace levels of plutonium. Test results showed that almost all of the enriched uranium will dissolve from the desicooler materials after extended boiling in one molar nitric acid solutions. The residue that contained uranium after completion of the extended boiling cycle consisted of brown solids that had agglomerated into large pieces and were floating on top of the dissolver solution. Addition of tenth molar fluoride to a three molar nitric acid solution containing boron did not dissolve remaining uranium from the brown solids. Only after boiling in an eight molar nitric acid-tenth molar fluoride solution without boron did remaining uranium and aluminum dissolve from the brown solids. The amount of uranium associated with brown solids would be approximately 1.4 percent of the total uranium content of the desicooler materials. The brown solids that remain in the First Uranium Cycle feed will accumulate at the organic/aqueous interface during solvent extraction operations. Most of the undissolved white residue that remained after extended boiling was aluminum oxide containing additional trace quantities of impurities. However, the presence of mercury used in H-Canyon dissolvers should complete the dissolution of these aluminum compounds.

Gray, J.H.

2003-06-23

297

Box Canyon Model Watershed Project : Annual Report 1997/1998.  

SciTech Connect

In 1997, the Kalispel Natural Resource Department (KNRD) initiated the Box Canyon Watershed Project. This project will concentrate on watershed protection and enhancement from an upland perspective and will complement current instream restoration efforts implemented through the Kalispel Resident Fish Project. Primary focus of this project is the Cee Cee Ah Creek watershed due to its proximity to the Reservation, importance as a traditional fishery, and potential for bull trout and west-slope cutthroat trout recovery.

Kalispel Natural Resource Department

1998-01-01

298

Canyon Creek: A late Pleistocene vertebrate locality in interior Alaska  

USGS Publications Warehouse

The Canyon Creek vertebrate-fossil locality is an extensive road cut near Fairbanks that exposes sediments that range in age from early Wisconsin to late Holocene. Tanana River gravel at the base of the section evidently formed during the Delta Glaciation of the north-central Alaska Range. Younger layers and lenses of fluvial sand are interbedded with arkosic gravel from Canyon Creek that contains tephra as well as fossil bones of an interstadial fauna about 40,000 years old. Solifluction deposits containing ventifacts, wedge casts, and rodent burrows formed during a subsequent period of periglacial activity that took place during the maximum phase of Donnelly Glaciation about 25,000-17,000 years ago. Overlying sheets of eolian sand are separated by a 9500-year-old paleosol that may correlate with a phase of early Holocene spruce expansion through central Alaska. The Pleistocene fauna from Canyon Creek consists of rodents (indicated by burrows), Mammuthus primigenius (woolly mammoth), Equus lambei (Yukon wild ass), Camelops hesternus (western camel), Bison sp. cf. B. crassicornis (large-horned bison), Ovis sp. cf. O. dalli (mountain sheep), Canis sp. cf. C. lupus (wolf), Lepus sp. cf. L. othus or L. arcticus (tundra hare), and Rangifer sp. (caribou). This assemblage suggests an open landscape in which trees and tall shrubs were either absent or confined to sheltered and moist sites. Camelops evidently was present in eastern Beringia during the middle Wisconsin interstadial interval but may have disappeared during the following glacial episode. The stratigraphic section at Canyon Creek appears to demonstrate that the Delta Glaciation of the north-central Alaska Range is at least in part of early Wisconsin age and was separated from the succeeding Donnelly Glaciation by an interstadial rather than interglacial episode. ?? 1981.

Weber, F. R.; Hamilton, T. D.; Hopkins, D. M.; Repenning, C. A.; Haas, H.

1981-01-01

299

Landslides and debris flows in Ephraim Canyon, central Utah  

SciTech Connect

The geology of 36 km{sup 2} in Ephraim Canyon, on the west side of the Wasatch Plateau, central Utah, was mapped at a scale of 1:12,000 following the occurrence of numerous landslides in 1983. The geologic map shows the distribution of the landslides and debris flows of 1983-86, as well as older landslide deposits, other surficial deposits, and bedrock. Several of the recent landslides are described and illustrated by means of maps or photographs.

Baum, R.L.; Fleming, R.W.

1989-01-01

300

Litter in submarine canyons off the west coast of Portugal  

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

301

Measurements of velocity and discharge, Grand Canyon, Arizona, May 1994  

USGS Publications Warehouse

The U.S. Geological Survey (USGS) evaluated the feasibility of utilizing an acoustic Doppler current profiler (ADCP) to collect velocity and discharge data in the Colorado River in Grand Canyon, Arizona, in May 1994. An ADCP is an instrument that can be used to measure water velocity and discharge from a moving boat. Measurements of velocity and discharge were made with an ADCP at 54 cross sections along the Colorado River between the Little Colorado River and Diamond Creek. Concurrent measurements of discharge with an ADCP and a Price-AA current meter were made at three U.S. Geological Survey streamflow-gaging stations: Colorado River above the Little Colorado River near Desert View, Colorado River near Grand Canyon, and Colorado River above Diamond Creek near Peach Springs. Discharges measured with an ADCP were within 3 percent of the rated discharge at each streamflow-gaging station. Discharges measured with the ADCP were within 4 percent of discharges measured with a Price-AA meter, except at the Colorado River above Diamond Creek. Vertical velocity profiles were measured with the ADCP from a stationary position at four cross sections along the Colorado River. Graphs of selected vertical velocity profiles collected in a cross section near National Canyon show considerable temporal variation among profile.

Oberg, Kevin, A.; Fisk, Gregory, G.

1995-01-01

302

Landslide assessment of Newell Creek Canyon, Oregon City, Oregon  

SciTech Connect

A study has been conducted in Newell Creek Canyon near Oregon City, Oregon, T3S, T2S, R2E. A landslide inventory has located 53 landslides in the 2.8 km[sup 2] area. The landslides range in area from approximately 15,000m[sup 2] to 10m[sup 2]. Past slides cover an approximate 7% of the canyon area. Landslide processes include: slump, slump-translational, slump-earthflow and earthflow. Hard, impermeable clay-rich layers in the Troutdale Formation form the failure planes for most of the slides. Slopes composed of Troutdale material may seem to be stable, but when cuts and fills are produced, slope failure is common because of the perched water tables and impermeable failure planes. Good examples of cut and fill failures are present on Highway 213 which passes through Newell Creek Canyon. Almost every cut and fill has failed since the road construction began. The latest failure is in the fill located at mile-post 2.1. From data gathered, a slope stability risk map was generated. Stability risk ratings are divided into three groups: high, moderate and low. High risk of slope instability is designated to all landslides mapped in the slide inventory. Moderate risk is designated to slopes in the Troutdale Formation greater than 8[degree]. Low risk is designated to slopes in the Troutdale Formation less than 8[degree].

Growney, L.; Burris, L.; Garletts, D.; Walsh, K. (Portland State Univ., OR (United States). Dept. of Geology)

1993-04-01

303

Dam and geomorphological influences on colorado river waterbird distribution, Grand Canyon, Arizona, USA  

Microsoft Academic Search

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

Lawrence E. Stevens; Kimberly A. Buck; Bryan T. Brown; Natasha C. Kline

1997-01-01

304

Facies control of Mississippian Porosity, Whitney Canyon-Carter Creek field, Wyoming Overthrust belt  

Microsoft Academic Search

Mississippian Mission Canyon carbonates are the most prolific Paleozoic reservoir in the Wyoming Overthrust belt. At Whitney Canyon-Carter Creek field, the Mission Canyon Formation holds recoverable reserves of 240 million bbl of oil equivalent. Production comes from a 350-ft (107 m) gross interval of shallow-water shelf carbonates. Capping the reservoir interval is a 300-ft (91 m) section of anhydrite and

Charles E. Bartberger

1985-01-01

305

Colorado River sediment transport: 1. Natural sediment supply limitation and the influence of Glen Canyon Dam  

Microsoft Academic Search

Analyses of flow, sediment-transport, bed-topographic, and sedimentologic data suggest that before the closure of Glen Canyon Dam in 1963, the Colorado River in Marble and Grand Canyons was annually supply-limited with respect to fine sediment (i.e., sand and finer material). Furthermore, these analyses suggest that the predam river in Glen Canyon was not supply-limited to the same degree and that

David J. Topping; David M. Rubin; L. E. Vierra

2000-01-01

306

Disturbance, productivity and diversity in deep-sea canyons: A worm's eye view  

NASA Astrophysics Data System (ADS)

The abundance, diversity and assemblage structure of polychaetes from the Nazaré, Setúbal and Cascais Canyons along the Iberian Margin were studied as part of the EU project HERMES. A Dynamic Equilibrium Model (DEM) was used to identify the main environmental factors structuring the assemblages. Box corer and megacorer samples from upper (1000 m), middle (3400 m) and lower canyon (4300 m) settings were taken in each canyon. Polychaete abundances in the Nazaré and Setúbal Canyons were highest at 3400 m while in Cascais there were only slight differences between the various depths. Most of the polychaetes occurred in the top 5 cm of the sediment. Sample diversity both within and among the canyon sites did not differ statistically despite differences in the environmental settings, suggesting that small-scale heterogeneity at the scale of the sampler was similar at all sites. Species richness at the level of site was lowest at 3400 m sites in both the Nazaré and Setúbal Canyons. In contrast, species richness increased from 1000 m to ca. 3400 m and then again to 4300 m in the Cascais Canyon. The differences were linked to the physico-biogeochemical environment of each canyon. Analyses of physico-environmental variables indicated that the Nazaré mid-canyon sites were subject to high levels of disturbance and intermediate levels of productivity, accounting for high abundances and low species richness. Low disturbance and low productivity characterised the lower Nazaré Canyon site at 4300 m. Diversity results agreed with predictions of the DEM. However, the 4300 m site in the Setúbal Canyon did not conform to model predictions. Overall, while the Iberian Margin canyons demonstrated higher abundance and biomass than ‘open slope’ polychaete assemblages, they had lower species richness.

Paterson, Gordon L. J.; Glover, Adrian G.; Cunha, Marina R.; Neal, Lenka; de Stigter, Henko C.; Kiriakoulakis, Konstadinos; Billett, David S. M.; Wolff, George A.; Tiago, Aurea; Ravara, Ascensão; Lamont, Peter; Tyler, Paul

2011-12-01

307

Structural and Functional Analysis of Validoxylamine A 7?-phosphate Synthase ValL Involved in Validamycin A Biosynthesis  

PubMed Central

Validamycin A (Val-A) is an effective antifungal agent widely used in Asian countries as crop protectant. Validoxylamine A, the core structure and intermediate of Val-A, consists of two C7-cyclitol units connected by a rare C-N bond. In the Val-A biosynthetic gene cluster in Streptomyces hygroscopicus 5008, the ORF valL was initially annotated as a validoxylamine A 7?-phosphate(V7P) synthase, whose encoded 497-aa protein shows high similarity with trehalose 6-phosphate(T6P) synthase. Gene inactivation of valL abolished both validoxylamine A and validamycin A productivity, and complementation with a cloned valL recovered 10% production of the wild-type in the mutant, indicating the involvement of ValL in validoxylamine A biosynthesis. Also we determined the structures of ValL and ValL/trehalose complex. The structural data indicates that ValL adopts the typical fold of GT-B protein family, featuring two Rossmann-fold domains and an active site at domain junction. The residues in the active site are arranged in a manner homologous to that of Escherichia coli (E.coli) T6P synthase OtsA. However, a significant discrepancy is found in the active-site loop region. Also noticeable structural variance is found around the active site entrance in the apo ValL structure while the region takes an ordered configuration upon binding of product analog trehalose. Furthermore, the modeling of V7P in the active site of ValL suggests that ValL might have a similar SNi-like mechanism as OtsA.

Zheng, Lina; Zhou, Xiang; Zhang, Huaidong; Ji, Xiaofeng; Li, Lei; Huang, Lin; Bai, Linquan; Zhang, Houjin

2012-01-01

308

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

309

Evidence for remnants of ancient ice-rich deposits: Mangala Valles outflow channel, Mars  

Microsoft Academic Search

High-resolution spacecraft data reveal the presence of a distinctive unit on the upper reaches of the floor of Mangala Valles, an ancient outflow channel on Mars. In contrast to abundant evidence for scour, intense erosion, and hydro- dynamic shaping typical of the floors and margins of Mangala and other outflow channels, this unit is smooth-surfaced, has cuspate margins, is superposed

Joseph S. Levy; James W. Head

2005-01-01

310

Episodes of floods in Mangala Valles, Mars, from the analysis of HRSC, MOC and THEMIS images  

Microsoft Academic Search

The Mangala Valles is a 900-km long outflow channel system in the highlands adjacent to the south-eastern flank of the Tharsis bulge. This work was intended to answer the following two questions unresolved in previous studies: (1) Was there only one source of water (Mangala Fossa at the valley head which is one of the Medusae Fossae troughs or graben)

Alexander T. Basilevsky; Gerhard Neukum; Stephanie C. Werner; Alexander Dumke; Stephan van Gasselt; Thomas Kneissl; Wilhelm Zuschneid; Daniela Rommel; Lorenz Wendt; Mary Chapman; James W. Head; Ronald Greeley

2009-01-01

311

Juventae Chasma and Maja Valles, Mars: Further Evidence for Multiple Flooding Events  

Microsoft Academic Search

Introduction: In this study we investigate the age relationship of Juventae Chasma to the adjacent Maja Valles in order to gain a feasible explanation for the formation and evolution of rhythmic light-toned layered deposits (LLD). In this first step, we use impact crater size-frequency distributions for dating the planetary surface in the regions of interest. Juventae Chasma is located at

C. Gross; L. Wendt; A. Dumke; G. Neukum

2009-01-01

312

Antimicrobial activity of flavonoids in medicinal plants from Taf?? del Valle (Tucumán, Argentina)  

Microsoft Academic Search

Preliminary studies of flavonoids have been realised in five native species from Taf?? del Valle (Tucumán, Argentina) used in popular medicine. Most of compounds detected were flavonoids mono and dihydroxylated in B ring. Screening for antimicrobial activity against Gram positive and Gram negative microorganisms has been realised with Lippia turbinata, Satureja parvifolia, Sambucus peruviana, Verbena officinalis and Chenopodium graveolens. The

Nancy E. Hernández; M. L. Tereschuk; L. R. Abdala

2000-01-01

313

Origin of Warrego Valles: A Case Study for Fluvial Valley Formation on Early Mars.  

National Technical Information Service (NTIS)

Warrego Valles is one of the best examples of a well integrated fluvial valley system that formed early in the geological history of Mars, the lack of similar erosion elsewhere along the edge of Thaumasia plateau is not consistent with a formation by rain...

V. C. Gulick J. Dohm K. Tanaka T. Hare

2000-01-01

314

Tectonic pressurization of aquifers in the formation of Mangala and Athabasca Valles, Mars  

Microsoft Academic Search

Mangala and Athabasca Valles are the type examples of a distinct class of outflow channels that debouch directly from extensional tectonic features. We here demonstrate that the tectonic events responsible for the formation of the graben and fissures at the sources of the channels would have likely resulted in a near-instantaneous pressurization of the surrounding aquifers. Subsequent drainage of the

Jeffrey C. Hanna; Roger J. Phillips

2006-01-01

315

Channeling episodes of Kasei Valles, Mars, and the nature of ridged plains material  

NASA Astrophysics Data System (ADS)

The geologic mapping compiled at 1:500,000 scale of the northern Kasei Valles area of Mars (MTMs 25062 and 25067) indicates (1) at least three periods of Kasei Valles channeling, (2) the development of Sacra Fossae (linear depressions on Tempe Terra and Lunae Planum) in relation to Kasei channeling episodes, and (3) the nature of ridged plains material dissected by Kasei Valles on northern Lunae Planum. (The three channeling periods consists of two flood events and a later, sapping related event). These findings suggest hydrologic conditions and processes that formed Kasei Valles and associated features and terrains. It is concluded that an early period of flooding, whose source is perhaps buried beneath lava flows of Tharsis Montes, may have eroded streamlined features in northern Lunae Planum. Also, later floods originating from Echus Chasma formed after the initial flooding and the mesas adjacent to the plateau. The Sacra Fossae formed after the initial flooding and during the second flooding by sapping, outbreak, scarp retreat, and collapse along joints and fractures in ridged plains materials.

Chapman, Mary G.; Tanaka, Kenneth L.

1991-06-01

316

Comment on "Athabasca Valles, Mars: a lava-draped channel system".  

PubMed

Jaeger et al. (Reports, 21 September 2007, p. 1709) presented images of the Athabasca Valles channel system on Mars and asserted that the observed deposits are composed of thin, fluid lavas. However, all the features they described are secondary and postdate the surface by many millions of years, as documented by structural relationships with small, young impact craters. PMID:18566267

Page, David P

2008-06-20

317

Canyon Effects on Nearshore Infragravity Waves During NCEX  

NASA Astrophysics Data System (ADS)

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

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

2004-12-01

318

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

319

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

SciTech Connect

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

Rossen, C.; Sarg, J.F.

1987-05-01

320

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

NASA Astrophysics Data System (ADS)

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

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

2009-04-01

321

Restoring Anadromous Fish Habitat in Big Canyon Creek Watershed; Anadromous Fish Habitat Restoration in the Nichols Canyon Subwatershed, 2000 Annual Report.  

SciTech Connect

Nez Perce Soil & Water Conservation District (NPSWCD) undertook the Nichols Canyon Subwatershed Steelhead Trout Habitat Improvement Project in the spring of 1999 with funding from a grant through the Bonneville Power Administration. The Project's purpose is to install and implement agricultural best management practices (MBPS) and riparian restorations with the goal of improving steelhead trout spawning and rearing habitat in the subwatershed. Improvements to fish habitat in the Big Canyon Creek tributaries enhances natural production of the species in Big Canyon Creek and ultimately the Clearwater River. This report is a summation of the progress made by the NPSWCD in the Project's second year.

Koziol, Deb (Nez Perce Soil and Water Conservation District, Lewiston, ID)

2001-02-01

322

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

323

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

PubMed Central

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

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

2010-01-01

324

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

SciTech Connect

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

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

1990-07-01

325

78 FR 34894 - Regulated Navigation Area, Gulf of Mexico: Mississippi Canyon Block 20, South of New Orleans, LA...  

Federal Register 2010, 2011, 2012, 2013

...1625-AA11 Regulated Navigation Area, Gulf of Mexico: Mississippi Canyon Block 20, South of New Orleans, LA; Correction AGENCY...resulted from Hurricane Ivan's storm surge that toppled the Mississippi Canyon (MC) 20 Platform A. The platform's wells were...

2013-06-11

326

75 FR 18201 - Juniper Canyon Wind Power, LLC; Supplemental Notice That Initial Market-Based Rate Filing...  

Federal Register 2010, 2011, 2012, 2013

...Commission [Docket No. ER10-975-000] Juniper Canyon Wind Power, LLC; Supplemental Notice That Initial Market-Based...in the above-referenced proceeding of Juniper Canyon Wind Power, LLC's application for market-based rate...

2010-04-09

327

75 FR 54920 - In the Matter of Pacific Gas & Electric Company (Diablo Canyon Nuclear Power Plant, Units 1 and 2...  

Federal Register 2010, 2011, 2012, 2013

...for the Diablo Canyon Nuclear Power Plant, Units 1 and 2, near...On January 21, 2010, the Nuclear Regulatory Commission (NRC...an understanding of seismic risks to the Diablo Canyon nuclear power plant. Further, that...

2010-09-09

328

76 FR 9347 - Coyote Canyon Energy LLC; Supplemental Notice That Initial Market-Based Rate Filing Includes...  

Federal Register 2010, 2011, 2012, 2013

...Energy Regulatory Commission [Docket No. ER11-2860-000] Coyote Canyon Energy LLC; Supplemental Notice That Initial Market-Based...supplemental notice in the above-referenced proceeding of Coyote Canyon Energy LLC's application for market-based rate...

2011-02-17

329

Geothermal data for 95 thermal and nonthermal waters of the Valles Caldera - southern Jemez Mountains region, New Mexico  

SciTech Connect

Field, chemical, and isotopic data for 95 thermal and nonthermal waters of the southern Jemez Mountains, New Mexico are presented. This region includes all thermal and mineral waters associated with Valles Caldera and many of those located near the Nacimiento Uplift, near San Ysidro. Waters of the region can be categorized into five general types: (1) surface and near surface meteoric waters; (2) acid-sulfate waters (Valles Caldera); (3) thermal meteoric waters (Valles Caldera); (4) deep geothermal and derivative waters (Valles Caldera); and (5) mineralized waters near San Ysidro. Some waters display chemical and isotopic characteristics intermediate between the types listed. The object of the data is to help interpret geothermal potential of the Jemez Mountains region and to provide background data for investigating problems in hydrology, structural geology, hydrothermal alterations, and hydrothermal solution chemistry.

Goff, F.; McCormick, Trujillo, P.E. Jr.; Counce, D.; Grigsby, C.O.

1982-05-01

330

Coupling Viking Information with Themis and Mola Data Results in Significant Improvement in Paleoerosional Detail of Warrego Valles  

NASA Astrophysics Data System (ADS)

Here we report preliminary findings on the re-evaluation of the Viking-based, published geologic map information of the Thaumasia region through detailed investigation of the Warrego rise region, which includes Warrego Valles.

Dohm, J. M.; Hare, T. M.

2009-03-01

331

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

332

Recirculating flow and sedimentation in the Colorado River in Grand Canyon, Arizona  

Microsoft Academic Search

Debris fans debouching into the bottom of Grand Canyon create rapids and flow separation in the Colorado River. The patterns of flow and the behavior of recirculation zones formed by flow separation are consistent throughout the Canyon's length. Zones of recirculating flow occur along the margin of channel expansions. Recirculation zones are comprised of one primary eddy; secondary eddies and

John C. Schmidt

1990-01-01

333

Unsaturated Groundwater Flow Beneath Upper Mortandad Canyon, Los Alamos, New Mexico  

Microsoft Academic Search

Mortandad Canyon is a discharge site for treated industrial effluents containing radionuclides and other chemicals at Los Alamos National Laboratory, New Mexico. This study was conducted to develop an understanding of the unsaturated hydrologic behavior below the canyon floor. The main goal of this study was to evaluate the hypothetical performance of the vadose zone above the water table. Numerical

Dander

1998-01-01

334

Combined optic-flow and stereo-based navigation of urban canyons for a UAV  

Microsoft Academic Search

We present a novel vision-based technique for navigating an unmanned aerial vehicle (UAV) through urban canyons. Our technique relies on both optic flow and stereo vision information. We show that the combination of stereo and optic flow (stereo flow) is more effective at navigating urban canyons than either technique alone. Optic flow from a pair of sideways looking cameras is

Stefan Hrabar; Gaurav S. Sukhatme; Peter Corke; Kane Usher; Jonathan Roberts

2005-01-01

335

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

Microsoft Academic Search

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

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

2009-01-01

336

Grandview and Hermit Trails Historical Research Study, Grand Canyon National Park, Arizona.  

National Technical Information Service (NTIS)

Grand Canyon National Park, located in northwestern Arizona, is one of the oldest and most spectacular of our national parks. Established by act of Congress, and signed into law by President Wilson on February 26, 1919, Grand Canyon National Park, in its ...

D. Sutphen

1990-01-01

337

Side-scan Sonar Imaging of the Colorado River, Grand Canyon.  

National Technical Information Service (NTIS)

This paper presents data collection methods and side-scan sonar data collected along the Colorado River in Grand Canyon in August and September of 2000. The purpose of the data collection effort was to image the distribution of sand between Glen Canyon Da...

D. Hogg F. L. Wong P. Galanis R. Anima

2007-01-01

338

Tar sand occurrences in the Bush Butte Quadrangle, Wyoming, with emphasis on the Trapper Canyon Deposit  

Microsoft Academic Search

The Trapper Canyon Tar Sand Deposit is located in the eastern Bighorn Basin, approximately 25 miles east of Greybull, Wyoming. This project not only involved detailed geologic mapping of the Trapper Canyon Tar Sand Deposit, but also sampling and describing the tar zone as well as the bounding barren zones. Samples were analyzed for porosity, permeability, oil saturation, and characteristics

A. J. VerPloeg; R. H. DeBruin

1983-01-01

339

Restoring Anadromous Fish Habitat in Big Canyon Creek Watershed, 2002 Summary Report  

Microsoft Academic Search

Nez Perce Soil and Water Conservation District (NPSWCD) developed the ''Anadromous Fish Habitat Restoration in the Nichols Canyon Subwatershed'' project to assist in the enhancement of anadromous fish natural production in the Big Canyon watershed by improving salmonid spawning and rearing habitats. The project began in 1999. NPSWCD seeks to assist private, tribal, county, and state landowners in implementing Best

Koziol; Deb

2002-01-01

340

Geophysical Exploration of the Red Rocks Canyon Landfill in Colorado Springs, Colorado  

Microsoft Academic Search

Our introductory geophysics class conducted a survey of the Red Rocks Canyon landfill to determine its boundaries, depth, type of fill, and groundwater runoff patterns. In the 1970s and 1980s the canyon was filled with domestic waste, and has recently been acquired by the city to extend an existing park. Our results in general portray a heterogenous subsurface and reveal

N. Calhoun; C. Morin; S. Gy; C. Bank

2005-01-01

341

The role of radiative-convective interaction in creating the microclimate of urban street canyons  

Microsoft Academic Search

An approximate sky view factor (SVF) has been developed, which is capable of estimating the mean rate of net longwave radiant energy loss from urban street canyons. Reduced scale models of typical canyon geometries were used in outdoor tests to verify the predictions of radiant fluxes obtained using the proposed SVF.

Hanna Swaid

1993-01-01

342

Small mammal study of Sandia Canyon, 1994 and 1995  

SciTech Connect

A wide range of plant and wildlife species utilize water discharged from facilities at Los Alamos National Laboratory (LANL). The purpose of this study was to gather baseline data of small mammal populations and compare small mammal characteristics within three areas of Sandia Canyon, which receives outfall effluents from multiple sources. Three small mammal trapping webs were placed in the upper portion of Sandia Canyon, the first two were centered in a cattail-dominated marsh with a ponderosa pine overstory and the third web was placed in a much drier transition area with a ponderosa pine overstory. Webs 1 and 2 had the highest species diversity indices with deer mice the most commonly captured species in all webs. However, at Web 1, voles, shrews, and harvest mice, species more commonly found in moist habitats, made up a much greater overall percentage (65.6%) than did deer mice and brush mice (34.5%). The highest densities and biomass of animals were found in Web 1 with a continual decrease in density estimates in each web downstream. There is no statistical difference between the mean body weights of deer mice and brush mice between sites. Mean body length was also determined not to be statistically different between the webs (GLM [deer mouse], F = 0.89, p = 0.4117; GLM [brush mouse], F = 2.49, p = 0.0999). Furthermore, no statistical difference between webs was found for the mean lean body masses of deer and brush mice (GLM [deer mouse], F = 2.54, p = 0.0838; GLM [brush mouse], F = 1.60, p = 0.2229). Additional monitoring studies should be conducted in Sandia Canyon so comparisons over time can be made. In addition, rodent tissues should be sampled for contaminants and then compared to background or control populations elsewhere at the Laboratory or at an off-site location.

Bennett, K.; Biggs, J.

1996-11-01

343

Comparisons of Water Quality and Biological Variables from Colorado River Shoreline Habitats in Grand Canyon, Arizona, under Steady and Fluctuating Discharges from Glen Canyon Dam.  

National Technical Information Service (NTIS)

Glen Canyon Dam operations are known to affect mainstem Colorado River temperature and shoreline habitats for native fish. Options for ameliorating the impacts that operations have on young native fish include changing release volumes and/or changing the ...

B. E. Ralston M. V. Lauretta T. A. Kennedy

2007-01-01

344

78 FR 24987 - Regulated Navigation Area, Gulf of Mexico; Mississippi Canyon Block 20, South of New Orleans, LA  

Federal Register 2010, 2011, 2012, 2013

...Navigation Area, Gulf of Mexico; Mississippi Canyon Block 20, South of New Orleans...Regulated Navigation Area (RNA) in the Mississippi Canyon Block 20 in the Gulf of Mexico...Ivan's storm surge that toppled the Mississippi Canyon (MC) 20 Platform A. The...

2013-04-29

345

78 FR 59234 - Regulated Navigation Area, Gulf of Mexico: Mississippi Canyon Block 20, South of New Orleans, LA  

Federal Register 2010, 2011, 2012, 2013

...Navigation Area, Gulf of Mexico: Mississippi Canyon Block 20, South of New Orleans...Regulated Navigation Area (RNA) in the Mississippi Canyon Block 20 in the Gulf of Mexico...Ivan's storm surge that toppled the Mississippi Canyon (MC) 20 Platform A. The...

2013-09-26

346

Response to Comments on “Apatite 4He/3He and (U-Th)/He Evidence for an Ancient Grand Canyon”  

NASA Astrophysics Data System (ADS)

We reiterate that geological observations do not require Grand Canyon carving coeval with Colorado River integration. (U-Th)/He data from the western canyon, totaling 29 reproducible analyses from six samples and two labs, compellingly support an ancient canyon. Three dispersed analyses from one anomalous sample do not refute this conclusion, nor do the claimed shortcomings of our modeling have validity.

Flowers, R. M.; Farley, K. A.

2013-04-01

347

Response to Comments on "Apatite 4He/3He and (U-Th)/He Evidence for an Ancient Grand Canyon".  

PubMed

We reiterate that geological observations do not require Grand Canyon carving coeval with Colorado River integration. (U-Th)/He data from the western canyon, totaling 29 reproducible analyses from six samples and two labs, compellingly support an ancient canyon. Three dispersed analyses from one anomalous sample do not refute this conclusion, nor do the claimed shortcomings of our modeling have validity. PMID:23580513

Flowers, R M; Farley, K A

2013-04-12

348

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

NASA Astrophysics Data System (ADS)

The area density of cloud-to-ground (CG) lightning strokes reported by the NLDN near the Grand Canyon, Arizona, show strong variations near the canyon rim. The average area density of strokes outside the canyon is about 8-times larger than within the canyon, and there is a clear increase in the frequency of lightning attachments near the top edge of the canyon rim. If the attachments are made at or near the top of the rim, this could imply a very large attractive radius and unusually long upward leaders, perhaps produced by enhanced electric fields at the canyon rim just prior to ground termination. If the attachments are made along the face of the canyon near the rim, another possible explanation of the existing data, then the high area density near the rim and the low density within the canyon might be explained by the random spatial development of downward branches in the lightning leader just prior to attachment, interacting with the slope and protrusions along the canyon walls. This geometrical development might cause attachment to occur to the canyon walls before the lower-altitude leader channels can attach to the canyon floor. Two other possible factors are (1) the attenuation or distortion of the electromagnetic fields produced by the lightning due to propagation from deep within the canyon to the surface and (2) a difficulty for lightning-producing storms to form over or propagate into the wider regions of the canyon. The effects of EM propagation will likely result in low-amplitude fields and/or produce waveforms that the NLDN will not classify as CG strokes. Storm-propagation effects will likely reduce the convection and the electrification of clouds over the wide portions of the canyon, and result in a lower area density of flashes. We will present limited results of some measurements that were obtained during July 2009 relating to each of the above factors, and we will outline our plans for additional measurements during July/August 2010 or 2011.

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

2009-12-01

349

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

350

Incision History of the Black Canyon of the Gunnison  

NASA Astrophysics Data System (ADS)

The Gunnison River is the major tributary of the Colorado River that drains some of the highest topography of the Colorado Rocky Mountains. Paleo river profiles at 640ka, 10Ma, and ~35Ma provide benchmarks to understand the long-term incision history of the Black Canyon. Reconstruction of these paleo profiles is based on elevated bedrock straths and alluvial deposits that can be dated using the Lava Creek B ash (640 ka), Grand Mesa and associated basalts (10 Ma), and Oligocene ash flow tuffs (~35 Ma). Comparison of these to the modern profile offers insight into incision history. The modern long profile displays a distinct knickpoint located near the Painted Wall in the Black Canyon of the Gunnison National Park. This high-gradient reach (10-km-long) is partly explained by the Vernal Mesa Granite, but it traverses basement lithologies present above and below the knickpoint, suggesting that increased river gradient is not explained entirely by hard bedrock. Incision rates downstream of the knickpoint are higher (250-300 m/Ma over 640 ka and ~ 150 m/Ma over 10 Ma) in comparison to upstream rates (140 m/Ma over 640 ka and ~ 150 m/Ma over 10 Ma). The difference in incision rates across the knickpoint argue that this feature reflects transient adjustment of the fluvial system to baselevel lowering associated with downstream drainage reorganization. Incision rates in the nearby reaches of the Colorado River since 1-3 Ma are distinctly higher than those in the time periods of ~30 Ma- present and 10 Ma-present. This leads us to infer that rapid incision was not established in the Gunnison region until post ca. 3 Ma. A knickpoint similar to that seen in the modern profile is present in the reconstructed 640ka profile, reinforcing the transient character and implying upstream migration of the knickpoint of 25km in the past 640 ka. Projection of the ~ 640 ka river gravels in the abandoned Shinn- Bostwick tributary to its intersection with the Gunnison at Red Canyon is presently the best constraint on the age of incision; here, ~400m of its ~700m total depth in the Black Canyon has been incised in the last 640 ka. To refine these profiles and incision rates, new mapping and sampling for cosmogenic burial dating have been conducted on major terraces at the North Fork Gunnison-Gunnison River confluence, the Shinn-Bostwick Park, and Grizzley Creek. These will provide new dates, confirm tephrochronolgic associations, and refine preexisting data to further constrain incision history.

Sandoval, M.; Karlstrom, K. E.; Aslan, A.; Kirby, E.; Granger, D.

2006-12-01

351

Ordering Geologic Events and Interpreting Geologic History: The Grand Canyon  

NSDL National Science Digital Library

This activity is designed to help students recognize the connections among things like rock identification and map reading with the "story" that these things can tell us in terms of geologic history. Students have already learned about using observation to identify rocks and the principles of interpreting geologic cross-sections. The activity gives students practice in rock ID, topo map reading, geologic map reading and the aspects of geologic time. Students work with rock samples and a geologic map of the Grand Canyon to interpret a history for the area.

Wenner, Jennifer

352

An exhumed Late Paleozoic canyon in the rocky mountains  

USGS Publications Warehouse

Landscapes are thought to be youthful, particularly those of active orogenic belts. Unaweep Canyon in the Colorado Rocky Mountains, a large gorge drained by two opposite-flowing creeks, is an exception. Its origin has long been enigmatic, but new data indicate that it is an exhumed late Paleozoic landform. Its survival within a region of profound late Paleozoic orogenesis demands a reassessment of tectonic models for the Ancestral Rocky Mountains, and its form and genesis have significant implications for understanding late Paleozoic equatorial climate. This discovery highlights the utility of paleogeomorphology as a tectonic and climatic indicator. ?? 2007 by The University of Chicago. All rights reserved.

Soreghan, G. S.; Sweet, D. E.; Marra, K. R.; Eble, C. F.; Soreghan, M. J.; Elmore, R. D.; Kaplan, S. A.; Blum, M. D.

2007-01-01

353

Air pollutant retention within a complex of urban street canyons  

NASA Astrophysics Data System (ADS)

Epidemiological studies of health effects associated with ambient air pollution are subject to uncertainty in the effects estimates related to the spatial and temporal variability of ambient air pollution. This study examines meteorological and concentration decay data for an urban canopy in Oklahoma City, OK to develop a modeling approach that can be used to estimate spatiotemporal variability in contaminant retention that could add bias or uncertainty to epidemiological results. Concentration and microscale turbulent wind data from the Joint Urban 2003 study were reanalyzed to examine scaling relationships between contaminant residence time in urban street canyons, urban boundary layer winds, and urban topography. Street-level sulfur hexafluoride (SF6) concentration time series were reviewed to find time periods that included a peak and decay. Exponential decay curves were fitted to each period, and a characteristic residence time was derived from each model slope. That residence time was nondimensionalized by the ratio of mean urban boundary layer wind speed to height of the building just upwind of the street canyon in which the concentration was measured. Sonic detection and ranging (SODAR) data were used to assess atmospheric turbulence conditions at times concurrent with the concentration decay measurements. Reynolds number (Re) was calculated from the 15-min average wind velocity and ranged from 2.1 × 106 to 7.6 × 107. Nondimensional residence time (H) ranged from 3.7 to 996 with a median of 13.3. Inverse relationships were validated between H and Re and between H and the street canyon aspect ratio. These relationships provided a mechanism to understand time-varying ventilation within a street canyon. The results shown here were intended to demonstrate how scaling relationships derived from the transport equation can be used to provide rapid estimates of characteristic decay times for the purpose of estimating variability in the concentrations encountered in an urban environment. This could be a useful tool to reduce uncertainty in air pollution epidemiological study results related to spatial and temporal variability in urban concentrations.

Richmond-Bryant, J.; Isukapalli, S. S.; Vallero, D. A.

2011-12-01

354

Comparing the Grand Canyon of the East to the Western one  

NASA Astrophysics Data System (ADS)

The Grand Canyon of the West (GCW) is an internationally well-known geological world wonder of the South Western United States' Colorado Plateau. The Grand Canyon of the East is a similarly beautiful, less well-known, smaller canyon in the Devonian/Silurian sedimentary rocks of the western part of New York State in the Eastern United States. For the purpose of creating a comparative database to be used in the field, classroom and public education settings, features of New York's canyon, better known as Letchworth State Park (LSP) to Arizona's canyon, were collected, obtained, and recorded. We compared various numbers on rock formations, ages of the units, stream volume, and depth and age of canyon formation, erosion processes and other interesting geological features between the two canyons. The sedimentary rocks of both canyons tell the story of the conditions under which the rocks were laid onto the Earth's surface at the time. This study includes an evaluation of how the two canyons have formed including features we see in the strata. Literature research revealed that LSP is on the order of 10 times smaller than the Grand Canyon in various aspects. Genesee river is up to only 4 m deep while the Colorado River reaches depths of up to 30 m. The Genesee extends 25.3 km within its canyon, paling at the majestic 445.79km of the Colorado within its canyon. The depths of the two canyons also show how small LSP is in comparison to the GCW Letchworth canyon's depth is 0.17 km while GCW is 1.61 km. The width of LSP's canyon is 0.1 km while the Grand Canyons' is 28.97 km at their widest locations. Fieldwork in both canyons allowed for some comparison of the natural waterfall features within the canyons. With help from a laser range finder measurements were taken from the most prominent waterfalls of LSP and the Havasu creek. Rock formations were compared. While the periods of Precambrian to the middle Permian time are found in the GCW, the Silurian/Devonian formations are missing at the GCW. On the other hand, during this period of time, a warm shallow sea was present in WNY, as its shoreline transgressed and regressed over the land, it deposited the Silurian/Devonian rocks we see today. This study contains helpful information about geology, past life, and past environments of the two areas. LSP is often used as a field trip location of Western New York's geology educators having in mind similarities to the much further away Grand Canyon. However, even though it's nickname suggest a promising comparison, LSP turns out to be a beautiful yet tiny baby brother of the Grand Canyon of the West, both in size and age.

Gorom, J.; Martinez-Hackert, B.

2007-12-01

355

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

NASA Astrophysics Data System (ADS)

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

KäMpf, Jochen

2006-11-01

356

Surface heating in relation to air temperature, wind and turbulence in an urban street canyon  

NASA Astrophysics Data System (ADS)

Wind and temperature measurements from within and above a deep urban canyon (height/width = 2.1) were used to examine the thermal structure of air within the canyon, exchange of heat with the overlying atmosphere, and the possible impacts of surface heating on within-canyon air flow. Measurements were made over a range of seasons and primarily analysed for sunny days. This allowed the study of temperature differences between opposing canyon walls and between wall and air of more than 15°C in summer. The wall temperature patterns follow those of incoming solar radiation loading with a secondary daytime effect from the longwave exchange between the walls. In winter, the canyon walls receive little direct solar radiation, and temperature differences are largely due to anthropogenic heating of the building interiors. Cool air from aloft and heated air from canyon walls is shown to circulate within the canyon under cross-canyon flow. Roofs and some portions of walls heat up rapidly on clear days and have a large influence on heat fluxes and the temperature field. The magnitude and direction of the measured turbulent heat flux also depend strongly on the direction of flow relative to surface heating. However, these spatial differences are smoothed by the shear layer at the canyon top. Buoyancy effects from the heated walls were not seen to have as large an impact on the measured flow field as has been shown in numerical experiments. At night canyon walls are shown to be the source of positive sensible heat fluxes. The measurements show that materials and their location, as well as geometry, play a role in regulating the heat exchange between the urban surface and atmosphere.

Offerle, B.; Eliasson, I.; Grimmond, C. S. B.; Holmer, B.

2007-02-01

357

F-Canyon Suspension and Deactivation Safety Analysis Reports  

SciTech Connect

This paper describes Savannah River Site's compliance with the Department of Energy (DOE) direction to suspend current operations, transition to accommodate revised facility missions, and initiate operations to deactivate F-Canyon using a suspension and deactivation safety basis. This paper integrates multiple Workshop theme topics - Lessons Learned from the Safety Analysis Process, Improvements in Documenting Hazard and Accident Analysis, and Closure Issues - Decontamination and Decommissioning. The paper describes the process used to develop safety documentation to support suspension and deactivation activities for F-Canyon. Embodied are descriptive efforts that include development of intermediate and final ''end states'' (e.g., transitional operations), preparation of safety bases documents to support transition, performance of suspension and deactivation activities (e.g. solvent washing, tank/sump flushing, and laboratory waste processing), and downgrade of Safety Class and Safety Significant equipment. The reduction and/or removal of hazards in the facility result in significant risk (frequency times consequence) reduction to the public, site workers, and the environment. Risk reduction then allows the downgrade of safety class and safety significant systems (e.g., ventilation system) and elimination of associated surveillances. The downgrade of safety systems results in significant cost savings.

LOW, JM

2004-04-30

358

Evaluation of the RIO-IFDM-street canyon model chain  

NASA Astrophysics Data System (ADS)

Integration of all relevant spatial scales in concentration modeling is important for assessing the European limit values for NO2. The local NO2-concentrations are influenced by the regional background, the local emissions and the street canyon effects. Therefore, it is important to consistently combine all these contributions in the model setup which is used for such an assessment. In this paper, we present the results of an integrated model chain, consisting of an advanced measurement interpolation model, a bi-Gaussian plume model and a canyon model to simulate the street-level concentrations over the city of Antwerp, Belgium. The results of this model chain are evaluated against independent weekly averaged NO2 measurements at 49 locations in the city of Antwerp, during both a late autumn and a late spring week. It is shown that the model performed well, explaining between 62% and 87% of the spatial variance, with a RMSE between 5 and 6 ?g m?1 and small biases. In addition to this overall validation, the performance of different components in the model chain is shown, in order to provide information on the importance of the different constituents.

Lefebvre, W.; Van Poppel, M.; Maiheu, B.; Janssen, S.; Dons, E.

2013-10-01

359

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

NASA Astrophysics Data System (ADS)

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

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

2009-02-01

360

Landslide Hazard Mapping In Valle D'aosta Region (nw- Italy)  

Microsoft Academic Search

Valle d'Aosta Region (NW-Italy) during the last decade experienced exceptional rainfall events (maximum cumulate rainfall 740 mm during the 13-17 October 2000 event) which triggered landslide phenomena responsible for extens ive damage and casualties. Different types of slope movement are present in the study area, including deep -seated slope deformations, some of which threaten inhabited areas and anthropogenic infrastructures. Within

F. Bonetto; M. Giardino; M. Parise

2002-01-01

361

Antimicrobial activity of flavonoids in medicinal plants from Tafí del Valle (Tucumán, Argentina).  

PubMed

Preliminary studies of flavonoids have been realised in five native species from Tafí del Valle (Tucumán, Argentina) used in popular medicine. Most of compounds detected were flavonoids mono and dihydroxylated in B ring. Screening for antimicrobial activity against Gram positive and Gram negative microorganisms has been realised with Lippia turbinata, Satureja parvifolia, Sambucus peruviana, Verbena officinalis and Chenopodium graveolens. The total extracts of flavonoids of each plant were tested and four species studied showed antimicrobial activity. PMID:11025172

Hernández, N E; Tereschuk, M L; Abdala, L R

2000-11-01

362

Malacofauna continental holocena y paleoambientes en Villa Valle María (Diamante, Entre Ríos, Argentina)  

Microsoft Academic Search

The molluscan fauna recovered from Holocene continental sediments at Villa Valle María fossiliferous locality (Diamante, Entre Ríos, Argentina), eolian in origin and dated at 2,490±45 14C yrs. B.P. on Bulimulus sp, is reported. It represents the first illustrated record of Quaternary molluscs from loess sequences in Argentina. It is represented exclusively by land snails which belong to five gastropod families

Marina L. Aguirre; Sergio E. Miquel; C. Adrián González; Daniela Kröhling; Alejandro F. Zucol; Mariana Brea; Christopher Eastoe

2011-01-01

363

Mössbauer study of archaeological ceramics from Valle del Alto Sinu (Colombia)  

NASA Astrophysics Data System (ADS)

A physico-chemical characterization of ceramic samples from the arachaeological sites of El Cabrero, El Gallo, and El Frasquillo (Valle del Alto Sinú) is presented. Extensive use of Mössbauer spectroscopy data reveals that the currently used typological classification scheme of Dolmatoff is related to the production technology of the different artifacts. In addition, a model for firing conditions for “Rojo Sencillo”, “Tierra Impresa”, “Tierra Incisa”, and “Blanco” types of ceramics is proposed.

Useche, L. A.; Gaviria, S.; Alabart, J. R.; Fontcuberta, J.

1990-07-01

364

Paleomagnetic study of the Valle de Santiago volcanics, Michoacán-Guanajuato volcanic field, Mexico  

Microsoft Academic Search

The Valle de Santiago area of the Michoacán-Guanajuato volcanic field is characterized by a 7 km by 50 km NNW-SSE trending cluster of 20 maars, 13 in a smaller sub-area. This volcanic lineament may be associated with a pre-existing fault or zone of structural weakness, which is approximately normal to the regional structure of the Trans-Mexican volcanic belt (TMVB). One

Rosa María Uribe-Cifuentes; Jaime Urrutia-Fucugauchi

1999-01-01

365

Lithologic descriptions and temperature profiles of five wells in the southwestern Valles caldera region, New Mexico  

SciTech Connect

The subsurface stratigraphy and temperature profiles of the southern and western Valles caldera region have been well constrained with the use of data from the VC-1, AET-4, WC 23-4, PC-1 and PC-2 wells. Data from these wells indicate that thermal gradients west of the caldera margin are between 110 and 140)degrees)C/km, with a maximum gradient occurring in the bottom of PC-1 equal to 240)degrees)C/km as a result of thermal fluid flow. Gradients within the caldera reach a maximum of 350)degrees)C/km, while the maximum thermal gradient measured southwest of the caldera in the thermal outflow plume is 140)degrees)C/km. The five wells exhibit high thermal gradients (>60)deghrees)C/km) resulting from high conductive heat flow associated with the Rio Grande rift and volcanism in the Valles caldera, as well as high convective heat flow associated with circulating geothermal fluids. Gamma logs run in four of the five wells appear to be of limited use for stratigraphic correlations in the caldera region. However, stratigraphic and temperature data from the five wells provide information about the structure and thermal regime of the southern and western Valles caldera region. 29 refs., 9 figs. 2 tabs.

Shevenell, L.; Goff, F.; Miles, D.; Waibel, A.; Swanberg, C.

1988-01-01

366

Subsurface structure of Valles Caldera; a resurgent cauldron in northern New Mexico. [Abstract only  

SciTech Connect

Valles Caldera is a 1.1 My old silicic cauldron lying at the intersection of the Rio Grande rift and northeast-trending Jemez Lineament. Geothermal exploration in the caldera region during the last 10 years provides subsurface data which refine our knowledge of deep caldera structure, but raise some questions concerning current models of resurgent cauldrons. For example, a detailed gravity investigation using 730 stations (Segar, 1974) shows a circular negative gravity anomaly centered over the caldera (as expected) but also indicates a strong northeast-trending grain of fault blocks in pre-caldera rocks, that are generally down-faulted to the southeast toward the Rift. Gravity data do not define a diapir structure beneath the resurgent dome attributable to tumescent magma; instead of a northeast-trending horst underlies the Redondo Peak segment of the dome. Interpretation of stratigraphy from many geothermal wells suggests that the caldera and resurgent dome are floored by untilted fault blocks (Hulen and Nielson, 1982). In addition, drilling to Precambrian basement and depths of 3.2 km has not encountered a large intrusive rhyolite that might logically produce tumescence of the dome. The new data indicate that the subsurface structural configuration of Valles Caldera is controlled by pre-caldera tectonics and that a more complicated mechanism is required to explain the resurgent dome standing high inside the caldera. A refined mechanism of resurgence might be one result of CSDP drilling at Valles Caldera.

Goff, F.

1983-03-01

367

Pollutant Concentrations in Street Canyons of Different Aspect Ratio with Avenues of Trees for Various Wind Directions  

NASA Astrophysics Data System (ADS)

This study summarizes the effects of avenues of trees in urban street canyons on traffic pollutant dispersion. We describe various wind-tunnel experiments with different tree-avenue models in combination with variations in street-canyon aspect ratio W/ H (with W the street-canyon width and H the building height) and approaching wind direction. Compared to tree-free street canyons, in general, higher pollutant concentrations are found. Avenues of trees do not suppress canyon vortices, although the air ventilation in canyons is hindered significantly. For a perpendicular wind direction, increases in wall-average and wall-maximum concentrations at the leeward canyon wall and decreases in wall-average concentrations at the windward wall are found. For oblique and perpendicular wind directions, increases at both canyon walls are obtained. The strongest effects of avenues of trees on traffic pollutant dispersion are observed for oblique wind directions for which also the largest concentrations at the canyon walls are found. Thus, the prevailing assumption that attributes the most harmful dispersion conditions to a perpendicular wind direction does not hold for street canyons with avenues of trees. Furthermore, following dimensional analysis, an estimate of the normalized wall-maximum traffic pollutant concentration in street canyons with avenues of trees is derived.

Gromke, Christof; Ruck, Bodo

2012-07-01

368

Exploring Mars: Old, Relatively  

NSDL National Science Digital Library

This activity uses an image of landslides and craters at the wall of Valles Marineris on Mars to teach students how the notion of superposition can help to determine the sequence of events in a planet's geologic history.

369

Extracting Compositional Variation from Themis Data for Features with Large Topography on Mars Via Atmospheric Equalization.  

National Technical Information Service (NTIS)

We have developed a means of equalizing the atmospheric signature in Mars Odyssey Thermal Emission Imaging System (THEMIS) infrared data over regions with large topography such as the Valles Marineris (VM). This equalization allows for the analysis of com...

F. S. Anderson J. S. Drake V. E. Hamilton

2005-01-01

370

Effect of Aluminum Substitution on the Emissivity Spectra of Hematite  

NASA Astrophysics Data System (ADS)

There are small differences in the emissivity spectra of the martian hematite found in Sinus Meridiani, Aram Chaos, and Valles Marineris. We report here on the effects of aluminum substitution on the emissivity spectra of hematite.

Glotch, T. D.; Morris, R. V.; Christensen, P. R.

2002-03-01

371

Effect of Aluminum Substitution on the Emissivity Spectra of Hematite  

Microsoft Academic Search

There are small differences in the emissivity spectra of the martian hematite found in Sinus Meridiani, Aram Chaos, and Valles Marineris. We report here on the effects of aluminum substitution on the emissivity spectra of hematite.

T. D. Glotch; R. V. Morris; P. R. Christensen

2002-01-01

372

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

373

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

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

374

Rapid formation of a modern bedrock canyon by a single flood event  

NASA Astrophysics Data System (ADS)

Deep river canyons are thought to form slowly over geological time (see, for example, ref. 1), cut by moderate flows that reoccur every few years. In contrast, some of the most spectacular canyons on Earth and Mars were probably carved rapidly during ancient megaflood events. Quantification of the flood discharge, duration and erosion mechanics that operated during such events is hampered because we lack modern analogues. Canyon Lake Gorge, Texas, was carved in 2002 during a single catastrophic flood. The event offers a rare opportunity to analyse canyon formation and test palaeo-hydraulic-reconstruction techniques under known topographic and hydraulic conditions. Here we use digital topographic models and visible/near-infrared aerial images from before and after the flood, discharge measured during the event, field measurements and sediment-transport modelling to show that the flood moved metre-sized boulders, excavated ~7m of limestone and transformed a soil-mantled valley into a bedrock canyon in just ~3days. We find that canyon morphology is strongly dependent on rock type: plucking of limestone blocks produced waterfalls, inner channels and bedrock strath terraces, whereas abrasion of cemented alluvium sculpted walls, plunge pools and streamlined islands. Canyon formation was so rapid that erosion might have been limited by the ability of the flow to transport sediment. We suggest that our results might improve hydraulic reconstructions of similar megafloods on Earth and Mars.

Lamb, Michael P.; Fonstad, Mark A.

2010-07-01

375

Experimental simulation of air quality in street canyon under changes of building orientation and aspect ratio.  

PubMed

To assist validation of numerical simulations of urban pollution, air quality in a street canyon was investigated using a wind tunnel as a research tool under neutral atmospheric conditions. We used tracer gas techniques from a line source without buoyancy. Ethylene (C(2)H(4)) was used as the tracer gas. The street canyon model was formed of six parallel building rows of the same length. The flow and dispersion field was analyzed and measured using a hot-wire anemometer with split fiber probe and fast flame ionization detector. The diffusion flow field in the boundary layer within the street canyon was examined at different locations, with varying building orientations (?=90°, 112.5°, 135° and 157.5°) and street canyon aspect ratios (W/H=1/2, 3/4 and 1) downwind of the leeward side of the street canyon model. Results show that velocity increases with aspect ratio, and with ?>90°. Pollutant concentration increases as aspect ratio decreases. This concentration decreases exponentially in the vertical direction, and decreases as ? increases from 90°. Measured pollutant concentration distributions indicate that variability of building orientation and aspect ratio in the street canyon are important for estimating air quality in the canyon. The data presented here can be used as a comprehensive database for validation of numerical models. PMID:22760437

Yassin, Mohamed F; Ohba, Masaake

2012-07-04

376

Bryant Canyon fan system: An unconfined, large river-sourced system in the Northwestern Gulf of Mexico  

SciTech Connect

The high-relief sea floor of the northwestern Gulf of Mexico slope is pockmarked by salt-rimmed minibasins and dissected by channels and canyons. Analysis of multichannel seismic reflection data reveals that Bryant Canyon and its fan are an unconfined, fluvially sourced system associated with the ancestral Mississippi River. Bryant Canyon eroded an extensive bypassing cut on the slope and delivered sediments to the unconfined area of the base of slope where they formed a fan. The canyon incorporates several minibasins and shallow salt structures. The canyon cross sections are easily recognizable in the minibasins, but are partially or completely obliterated by salt tectonism where the canyon incised the shallow salt structures. Salt appears to have encroached upon the canyon after abandonment and restored the sea floor to its pre-canyon, low-relief profile. We interpreted three depositional units in the Pleistocene section of the Bryant Canyon Fan. The lower units are characterized by erosional surfaces or channels and mass-transport deposits. The top unit consists of low- to moderate-amplitude reflections with moderate continuity, suggesting relatively uniform deposition. The widespread occurrence of erosional surfaces and channels in the lower units may suggest extensive canyon activity during sea level falls. Decreased depositional energy from lower units upward indicates abandonment of the canyon or eastward shift of the ancestral Mississippi River. The Bryant Canyon Fan system contains several potential reservoir facies, including turbidites, trapped in high-relief minibasins during periods of less extensive canyon activity, that may exhibit good reservoir quality and massive sand occurring in canyon fill. Channel deposits and distal, unchannelized turbidites of the fan also may contain reservoir-quality sand. Mass-transport deposits with moderate- to high-amplitude reflections and levee deposits close to channels probably contain sand.

Lee, G.H. [Kunsan National Univ. (Korea, Democratic People`s Republic of); Watkins, J.S.; Bryant, W.R. [Texas A& M Univ., College Station, TX (United States)

1996-03-01

377

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

NASA Astrophysics Data System (ADS)

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

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

2005-08-01

378

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

379

Long-term surveillance plan for the Burro Canyon disposal cell, Slick Rock, Colorado  

SciTech Connect

This long-term surveillance plant (LTSP) describes the US Department of energy`s (DOE) long-term care program for the Uranium Mill Tailings Remediation Action (UMTRA) Project`s burro Canyon disposal cell in San Miguel County, Colorado. This LTSP describes the long-term surveillance program the DOE will implement to ensure that the Burro Canyon disposal cell performs as designed. The program is based on site inspections to identify threats to disposal cell integrity. No ground water monitoring will be required at the Burro Canyon disposal cell because the ground water protection strategy is supplemental standards based on low-yield from the upper-most aquifer.

NONE

1996-11-01

380

A section of the Paleozoic formations of the Grand Canyon at the Bass trail  

USGS Publications Warehouse

The thick series of horizontal strata of Paleozoic age which makes the greater part of the wall of the Grand Canyon is probably broadly familiar to more people than the strata exposed in any other area in the western United States. Each detail of form or color in the wall is so definitely associated with a bed or set of beds in the series that these strata are the very elements of the canyon landscape. Consequently they have been described not only by geologists but by many writers who have been interested in the Grand Canyon chiefly as a scenic spectacle.

Noble, L. F.

1923-01-01

381

The Canovas Canyon Rhyolite, Jemez Volcanic Field, New Mexico: Early Eruptions From A Large Silicic Magma System, or Not?  

NASA Astrophysics Data System (ADS)

The Canovas Canyon Rhyolite (CCR) represents the earliest major interval of rhyolitic volcanism in the Jemez Volcanic Field (JVF). The CCR consists of volcanic domes, flows, tuffs and shallow intrusions restricted to the southern JVF in an area of ~180 km2, close to the size of the adjacent Valles Caldera. There has been no previous study specifically focused on the CCR, however, reconnaissance level work has suggested that ages range widely from ~13 to 9 Ma and major/trace element chemistry is variable. This study was undertaken to constrain whether the CCR comprises multiple eruptions of independently produced magma batches, or alternatively the early development of a large-scale, long-lived silicic magma system in the JVF. New 40Ar/39Ar dates (n=9) yield a range of ages for CCR rhyolites from 12.4 Ma to <8.2 Ma, indicating that eruptions occurred over at least a 4.2 Ma interval. Four dated samples fall in the range 9.2- 9.9 Ma. SiO2 varies from 67.3 to 78.5 wt.%. Samples are classified as low- to high-silica rhyolite, with the exception of one which is a trachydacite. There is no systematic variation of either major or minor elements with decreasing age. No apparent fractional crystallization trends are defined by the data, including those samples which fall in the relatively narrow range of 9.2-9.9 Ma. Initial 87Sr/86Sr ratios range widely, varying between 0.704684 and 0.709791. Similarly, 143Nd/144Nd ratios define a range of ENd values between -0.39 and -4.08. 206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb ratios range between 17.830- 18.315, 15.510-15.553 and 37.637-38.098, respectively. There is no correlation between isotopic composition and age. Isotopically, most CCR is fairly primitive, overlapping with the range of basaltic compositions from the JVF. However, some samples exhibit evidence of crustal contamination, and the available data suggest lower crust was involved. The isotopic variability between samples precludes a common origin in a single magma system. These data indicate that the Canovas Canyon Rhyolite represents a series of independent melt batches erupted over a substantial interval of time early in the development of the ~15 Ma evolution of the JVF. There is no evidence that a substantial, long-lived magma system developed during CCR eruptions. This is likely due to a lack of sufficient time and influx of mafic magmas early in the history of the JVF to promote large-scale crustal anatexis. Crustal interactions which did occur were restricted to the lower crust, where mafic magmas ponded and evolved by assimilation and fractional crystallization.

Padmore, P.; Spell, T.

2008-12-01

382

Critical Climate Controls and Information Needs for the Glen Canyon Adaptive Management Program and Environmental Assessment in the Grand Canyon Region  

NASA Astrophysics Data System (ADS)

Climatic drivers of episodic to interdecadal variations to the observed changes in the flood magnitude, timing and spatial scales affect the sediment inputs to the Colorado River ecosystem. Since the 1963 closure of Glen Canyon Dam, the dominant sole major supplier of sand to the Colorado River in the upper portion of Grand Canyon is the Paria River, which supplies about 6% of the pre-dam supply of sand at the upstream boundary of Grand Canyon National Park. Sand is delivered by the Paria River during short-duration (< 24 hours), large magnitude (up to 300 cubic meters/second) floods that occur primarily during the warm season (July-October). The planning and decision processes in the Glen Canyon Dam Adaptive Management Program (GCD-AMP) strive to balance numerous, often competing, objectives, such as,water supply, hydropower generation, low flow maintenance, maximizing conservation of the tributary supplied sediment, endangered species recovery, and cultural resources. In this work, we focus on a key concern identified by the AMP, related to the timing and volume of sediment input into Grand Canyon. Adequate sediment inputs into the river ecosystem Canyon combined with active flow management, of the timed in the form of strategically timed bypass releases from Glen Canyon Dam, support the restoration and maintenance of sand bar habitats and instream ecology. Variability in regional precipitation distribution on multiple time scales is diagnosed with emphasis on understanding the relative role of East Pacific tropical storms, North Pacific sea surface temperatures, and subtropical moisture sources. On longer time scales, structured variations in the sediment supply imply a changing baseline for mean ecological and geomorphological conditions in the Canyon, counter to the static view taken in the current environmental impact assessments. Better understanding of the coupled climate-hydrologic variations on multiple time scales is increasingly recognized as critical input for adaptive management (both passive and active). In collaboration with the GCD-AMP, this work deliberately identifies the entry-points for predictive hydroclimatic information at appropriate lead times. From the standpoint of this active adaptive management program, lead climate information allows scientists and managers to anticipate geomorphic response from critical tributaries, that in turn trigger large-scale, experimental releases from Glen Canyon Dam. Similar future studies are planned for the Little Colorado River, as flood frequency in that larger drainage is tied to both the ecosystem's sand supply and the spawning success and recruitment of endangered humpback chub.

Melis, T. S.; Jain, S.; Topping, D. J.; Pulwarty, R. S.; Eischeid, J. K.

2005-12-01

383

Achieving quality excellence at the Diablo Canyon Nuclear Power Plant  

SciTech Connect

Quality assurance methods at the Diablo Canyon plant were transformed from the then typical industry practices that often alienated professional and technical people, as well as craftsmen and their foremen, to a cooperative method that allowed plant personnel to work together as a team. It has created an attitude to do it right the first time. The roles of quality professionals were expanded to include teaching and coaching to facilitate enhanced communication between and within functional organizations. This included regular presentations to managers and line personnel in an informal group participative atmosphere. These presentations have become widely known at the plant as quality awareness tailboard sessions. These presentations are intended to increase personnel sensitivity to the subject of quality and quality management. Economic achievement of excellence in quality is essential to remain competitive in today's marketplace. The proactive team-oriented approach of quality assurance achieves the bottom line of high quality with concurrently enhanced productivity and cost-effectiveness.

Skidmore, S.M.; Taggart, D.A.

1988-01-01

384

Grand Canyon Trekkers: school-based lunchtime walking program.  

PubMed

The incidence of childhood overweight is especially troubling among low income Latino youth. Grand Canyon Trekkers (GCT) was implemented as a quasi-experimental study in 10 Title 1 elementary schools with a large Latino population to examine the effects of a 16-week structured walking program on components of health-related physical fitness: Body Mass Index (BMI), waist circumference, and cardio-respiratory. Data on 1,074 research participants revealed no significance changes in BMI or waist circumference (p > .05); however, cardio-respiratory fitness increased by 37.1% over baseline. Cardiovascular fitness is an independent determinant of long-term health; therefore, the GCT program may have significantly improved the future health profile of the participants and decreased their risk of metabolic diseases. PMID:21123848

Hawthorne, Alisa; Shaibi, Gabriel; Gance-Cleveland, Bonnie; McFall, Sarah

2010-12-01

385

Kern Canyon virus: electron microscopic and immunological studies.  

PubMed

Kern Canyon virus (KCV), propagated in suckling mouse brain and cell culture, was examined by negative contrast and thin section electron microscopy. The virus was found to exhibit symmetry similar to other viruses of the Stomatoviridae family. The bullet-shaped virus particles had a mean length of 132 micron and were 73 micron in diameter. Cross striations, axial channels and surface projections were prominent. Virus maturation occurred on marginal cytoplasmic membranes with mature virions accumulating extracellularly. Complement fixation, virus neutralization, and immunodiffusion tests comparing KCV with other bullet-shaped viruses of animals confirmed the distinct antigenicity of the virus, whereas comparison of KCV with vesicular stomatitis virus in a density gradient ultracentrifugation experiment emphasized the physical basis for including KCV within the Stomatoviridae family of viruses. PMID:18614084

Murphy, F A; Fields, B N

1967-12-01

386

Is there excess argon in the Fish Canyon magmatic system?  

NASA Astrophysics Data System (ADS)

Some phenocrysts from the Fish Canyon Tuff (San Juan volcanic field, south-western Colorado, USA) have yielded anomalously old 40Ar/39Ar apparent ages and yet the sanidine ages are sufficiently reproducible to allow its use as an international standard. The eruption age of the Fish Canyon tuff has recently been determined by high precision analysis and recalibration of the decay constants based on the sanidine standard at 28.305 ± 0.036 Ma [1], slightly younger than the generally accepted U-Pb age. Previously, minerals from the tuff have been used in various geochronological studies e.g., fission-track; U-Pb; Rb-Sr; K-Ar and 40Ar/39Ar, but U-Pb zircon ages which range 28.37 - 28.61 Ma appear to be older than the sanidine and other minerals, including biotite, yield older ages (27.41 - 28.25 Ma for biotite) [2]. In the Fish Canyon volcanic system, the erupted products are thought to exist in the magma chamber for significant periods prior to eruption [3] and then pass rapidly from a high temperature magmatic environment (where Ar is free to re-equilibrate among the minerals), to effectively being quenched upon eruption (where Ar becomes immobile). Artificially elevated ages, older than eruption age, have been identified in some 40Ar/39Ar geochronological studies (e.g. [4]). These older ages may either reflect; 1) argon accumulation in pheno- or xenocrysts (by radioactive decay of parent 40K), 2) excess argon (40ArE) incorporated into a mineral during crystallisation (via diffusion into the mineral lattice or hosted within fluid or melt inclusions) or 3) inherited radiogenic argon (the dated material contains a component older than the age of eruption) [5]. To better understand the effects of 40ArE on 40Ar/39Ar apparent ages we have conducted a detailed study of intra-grain grain age variations by UV-LAMP Ar-analysis. Analysis of polished thick sections has been performed in-situ using a 213nm laser and Nu Instruments Noblesse which is able to discriminate against interfering peaks at mass 36 allowing us to correct for the atmospheric 40Ar content. By using this method to analyse potassium-rich minerals (sanidine and biotite) and potassium-poor minerals (quartz and plagioclase), it has been possible to study the distribution of argon within these mineral phases and its incorporation into melt, fluid and solid inclusions. Here we report new 40Ar/39Ar intra-grain age data of minerals from the Fish Canyon Tuff, which despite being well characterised and extensively researched has not yet been a subject for this particular technique. [1] Renne P. R. et al., (2010) Geochim. Cosmochim. Acta, 74, 5349-5367. [2] Bachmann, O. et al., (2007) Chemical Geology, 236, 134-166.[3] Charlier, B.L.A. et al., (2007) Journal of Petrology, 48, 1875-1894. [4] Esser, R. P. et al., (1997) Geochim. Cosmochim. Acta, 61, 3789-3801. [5] Kelley, S. (2002) Chemical Geology, 188, 1-22. Corresponding Author: c.m.wilkinson@open.ac.uk

Wilkinson, C. M.; Sherlock, S.; Kelley, S. P.; Charlier, B. L.

2010-12-01

387

RECALIBRATION OF H CANYON ONLINE SPECTROPHOTOMETER AT EXTENDED URANIUM CONCENTRATION  

SciTech Connect

The H Canyon online spectrophotometers are calibrated for measurement of the uranium and nitric acid concentrations of several tanks in the 2nd Uranium Cycle.[1] The spectrometers, flow cells, and prediction models are currently optimized for a process in which uranium concentrations are expected to range from 0-15 g/L and nitric acid concentrations from 0.05-6 M. However, an upcoming processing campaign will involve 'Super Kukla' material, which has a lower than usual enrichment of fissionable uranium. Total uranium concentrations will be higher, spanning approximately 0-30 g/L U, with no change in the nitric acid concentrations. The new processing conditions require the installation of new flow cells with shorter path lengths. As the process solutions have a higher uranium concentration, the shorter path length is required to decrease the absorptivity to values closer to the optimal range for the instrument. Also, new uranium and nitric acid prediction models are required to span the extended uranium concentration range. The models will be developed for the 17.5 and 15.4 tanks, for which nitric acid concentrations will not exceed 1 M. The restricted acid range compared to the original models is anticipated to reduce the measurement uncertainty for both uranium and nitric acid. The online spectrophotometers in H Canyon Second Uranium Cycle were modified to allow measurement of uranium and nitric acid for the Super Kukla processing campaign. The expected uranium concentrations, which are higher than those that have been recently processed, required new flow cells with one-third the optical path length of the existing cells. Also, new uranium and nitric acid calibrations were made. The estimated reading uncertainties (2{sigma}) for Tanks 15.4 and 17.5 are {approx}5% for uranium and {approx}25% for nitric acid.

Lascola, R

2008-10-29

388

Measuring Turbulent Wind Drag in Urban Street Canyons  

NASA Astrophysics Data System (ADS)

Computer models of turbulent transport rely on scaling terms such as the surface friction velocity, u*. Whether a model calculates u* from first principles, or uses a parameterized value, it is important to measure u* in the field in order to verify and validate any model. Traditional measures of u* over flat terrain are taken to be proportional to the vertical turbulent flux of the wind's momentum toward the earth's surface which is assumed to be horizontal and homogeneous. If measurement of u* is taken from high enough above the influence of complex surfaces such as rough vegetation or urban buildings, their effects can be ignored and the traditional measures of u* apply. Until recently, this was not a limitation because the lowest modeled levels were typically several roughness heights above the roughness elements. As models become finer scale and begin to resolve complex details such as urban street canyons, they continue to use scaling schemes and parameterizations similar to those used for the older coarser resolution models. Measurement of fluxes in these complex environments, however, becomes problematic as the influence of momentum loss to vertical surfaces becomes important and the standard definitions of u* no longer apply. To overcome the limitations of the standard measures of u*, the full Reynolds stress matrix is utilized to provide a scaling term that captures the spirit of u* while still taking into account the influence of vertical surfaces. By providing a more stable scaling term than the standard u*, model validation and verification are again possible. The usefulness of this new scaling term is shown with street canyon data taken during the JU2003 field campaign, in Oklahoma City, during July 2003.

Klipp, C. L.

2008-12-01

389

Submarine canyon and fan systems of the California Continental Borderland  

USGS Publications Warehouse

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

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

2009-01-01

390

Experimental Assessment of the Susceptibility of Aedes Mosquitoes (Diptera: Culicidae) to Infection with Jamestown Canyon Virus.  

National Technical Information Service (NTIS)

The susceptibility of the principal Aedes species mosquitoes of the Delmarva Peninsula to infection with Jamestown Canyon (JC) virus was assessed in a series of laboratory experiments. Data revealed that infection rates were 60% or greater for Aedes solli...

D. M. Watts G. G. Clark R. R. Pinger C. L. Crabbs

1986-01-01

391

Financial Analysis of Experimental Releases Conducted at Glen Canyon Dam During Water Year 2012.  

National Technical Information Service (NTIS)

This report examines the financial implications of experimental flows conducted at the Glen Canyon Dam (GCD) in water year 2012. It is the fourth report in a series examining financial implications of experimental flows conducted since the Record of Decis...

2012-01-01

392

Ecological and Physiological Implications of Greenbelt Irrigation. Progress Report of the Maloney Canyon Project - 1974.  

National Technical Information Service (NTIS)

The multipurpose nature of a waste water irrigated greenbelt such as Maloney Canyon dictates the establishment of extensive research into the response of components of plant, soil, and water systems to the application of effluent irrigation. The purpose o...

V. B. Youngner T. E. Williams L. R. Green

1974-01-01

393

Black Canyon of the Gunnison National Monument and Curecanti National Recreation Area. General Management Plan.  

National Technical Information Service (NTIS)

Curecanti National Recreation Area and Black Canyon of the Gunnison National Monument are directly adjacent to one another and are linked as part of the larger Gunnison River Basin ecosystem. The purpose of this environmental assessment is to provide suff...

1996-01-01

394

General Management Plan. Black Canyon of the Gunnison National Monument and Curecanti National Recreation Area.  

National Technical Information Service (NTIS)

Curecanti National Recreation Area and Black Canyon of the Gunnison National Monument are directly adjacent to one another and are linked ecologically as part of the larger Gunnison River Basin ecosystem. Yet each park has a very different purpose. Togeth...

1997-01-01

395

33. SAR1, LOOKING DOWN CANYON OVER TAILRACE CONSTRUCTION. EEC print ...  

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

33. SAR-1, LOOKING DOWN CANYON OVER TAILRACE CONSTRUCTION. EEC print no. G-C-01-00269, no date. Photograph by Benjamin F. Pearson. - Santa Ana River Hydroelectric System, SAR-1 Powerhouse, Redlands, San Bernardino County, CA

396

Strain and Tilt Changes Associated with the Stone Canyon Earthquake of September 4, 1972.  

National Technical Information Service (NTIS)

Strainmeters and tiltmeters near the magnitude 4.7 Stone Canyon earthquake of September 4, 1972, recorded strain and tilt steps during the earthquake, followed by a creep-like episode of one hour's duration. (Author)

C. Bufe D. Tocher

1972-01-01

397

Integrated Project Management Planning for the Deactivation of the Savannah River Site F-Canyon Complex  

SciTech Connect

This paper explains the planning process that is being utilized by the Westinghouse Savannah River Company to take the F-Canyon Complex facilities from operations to a deactivated condition awaiting final decommissioning.

Clark, T.G.

2000-12-01

398

Archaeological Test and Data Recovery Program at Telegraph Canyon, Chula Vista, California.  

National Technical Information Service (NTIS)

A series of four mechanically dug trenches were excavated and analyzed with regard to subsurface cultural content along the channeled creekbed at the mouth of Telegraph Canyon in Chula Vista, California. The first phase of testing was conducted on Septemb...

W. T. Eckhartdt R. L. Carrico

1978-01-01

399

Lizards Along the Colorado River in Grand Canyon National Park: Possible Effects of Fluctuating River Flows,  

National Technical Information Service (NTIS)

Distribution, abundance, and reproduction of selected reptilian species were studied in riparian habitats along the Colorado River in Grand Canyon National Park. Shoreline and near-shore riparian habitats were found to support the highest densities and hi...

P. L. Warren C. R. Schwalbe

1986-01-01

400

Bighorn Canyon National Recreation Area, Montana-Wyoming. Volume 1 and 2.  

National Technical Information Service (NTIS)

The report provides basic data of general interest concerning Bighorn Canyon National Recreation Area. Within the limits of the area there are many and diverse historic sites. These have been identified, evaluated, and plotted on historical base maps. Thi...

E. C. Bearss

1970-01-01

401

Influence of a dam on fine-sediment storage in a canyon river  

USGS Publications Warehouse

Glen Canyon Dam has caused a fundamental change in the distribution of fine sediment storage in the 99-km reach of the Colorado River in Marble Canyon, Grand Canyon National Park, Arizona. The two major storage sites for fine sediment (i.e., sand and finer material) in this canyon river are lateral recirculation eddies and the main-channel bed. We use a combination of methods, including direct measurement of sediment storage change, measurements of sediment flux, and comparison of the grain size of sediment found in different storage sites relative to the supply and that in transport, in order to evaluate the change in both the volume and location of sediment storage. The analysis shows that the bed of the main channel was an important storage environment for fine sediment in the predam era. In years of large seasonal accumulation, approximately 50% of the fine sediment supplied to the reach from upstream sources was stored on the main-channel bed. In contrast, sediment budgets constructed for two short-duration, high experimental releases from Glen Canyon Dam indicate that approximately 90% of the sediment discharge from the reach during each release was derived from eddy storage, rather than from sandy deposits on the main-channel bed. These results indicate that the majority of the fine sediment in Marble Canyon is now stored in eddies, even though they occupy a small percentage (???17%) of the total river area. Because of a 95% reduction in the supply of fine sediment to Marble Canyon, future high releases without significant input of tributary sediment will potentially erode sediment from long-term eddy storage, resulting in continued degradation in Marble Canyon. Copyright 2006 by the American Geophysical Union.

Hazel, Jr. , J. E.; Topping, D. J.; Schmidt, J. C.; Kaplinski, M.

2006-01-01

402

Construction of a large span concrete roof over a vitrification building canyon  

Microsoft Academic Search

An innovative shoring system for a 1.22 m (4-foot) thick concrete roof spanning 71 feet is discussed. At a height of 22.3 m (73 ft) from the canyon floor, conventional shoring using scaffolding was not cost-effective and would have interrupted construction in the canyon. High shoring would have also been a safety hazard. The shoring method utilized consists of roof

I. K. Ghosh; C. D. Alexandrou; H. W. Tom

1988-01-01

403

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

Microsoft Academic Search

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

N. Skliris; G. Lacroix; S. Djenidi

2004-01-01

404

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

Microsoft Academic Search

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

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

2010-01-01

405

Side-Scan Sonar Imaging of the Colorado River, Grand Canyon  

USGS Publications Warehouse

This paper presents data collection methods and side-scan sonar data collected along the Colorado River in Grand Canyon in August and September of 2000. The purpose of the data collection effort was to image the distribution of sand between Glen Canyon Dam and river mile 87.4 before and after the 31,600 cfs flow of September 6-8. The side-scan sonar imaging focused on pools between rapids but included smaller rapids where possible.

Anima, Roberto; Wong, Florence L.; Hogg, David; Galanis, Peter

2007-01-01

406

Integrated modeling of pedestrian energy exchange and thermal comfort in urban street canyons  

Microsoft Academic Search

An open-air scale model is used to quantify pedestrian radiative and convective energy exchanges in street canyons of varying geometry, as well as surface-atmosphere energy exchanges above the urban canopy. A semi-empirical model based on measured data in summer is developed to link between the two levels, for the prediction of pedestrian energy exchange within a given street canyon based

D. Pearlmutter; P. Berliner; E. Shaviv

2007-01-01

407

Colorado River sediment transport 1. Natural sediment supply limitation and the influence of Glen Canyon Dam  

USGS Publications Warehouse

Analyses of flow, sediment-transport, bed-topographic, and sedimentologic data suggest that before the closure of Glen Canyon Dam in 1963, the Colorado River in Marble and Grand Canyons was annually supply-limited with respect to fine sediment (i.e., sand and finer material). Furthermore, these analyses suggest that the predam river in Glen Canyon was not supply-limited to the same degree and that the degree of annual supply limitation increased near the head of Marble Canyon. The predam Colorado River in Grand Canyon displays evidence of four effects of supply limitation: (1) seasonal hysteresis in sediment concentration, (2) seasonal hysteresis in sediment grain size coupled to the seasonal hysteresis in sediment concentration, (3) production of inversely graded flood deposits, and (4) development or modification of a lag between the time of a flood peak and the time of either maximum or minimum (depending on reach geometry) bed elevation. Analyses of sediment budgets provide additional support for the interpretation that the predam river was annually supply-limited with respect to fine sediment, but it was not supply-limited with respect to fine sediment during all seasons. In the average predam year, sand would accumulate and be stored in Marble Canyon and upper Grand Canyon for 9 months of the year (from July through March) when flows were dominantly below 200-300 m3/s; this stored sand was then eroded during April through June when flows were typically higher. After closure of Glen Canyon Dam, because of the large magnitudes of the uncertainties in the sediment budget, no season of substantial sand accumulation is evident. Because most flows in the postdam river exceed 200-300 m3/s, substantial sand accumulation in the postdam river is unlikely.

Topping, D. J.; Rubin, D. M.; Vierra, Jr. , L. E.

2000-01-01

408

Large-Eddy Simulation of Flow and Scalar Transport in a Modeled Street Canyon  

Microsoft Academic Search

This study uses large-eddy simulation (LES) to illustrate the flow and turbulence structure and to investigate the mechanism of passive scalar transport in a street canyon. Calculations for a modeled street canyon with building-height-to-street-width ratio of unity at Reynolds number equal to 12 000 are conducted. When the approaching wind is perpendicular to the street axis, the calculation produces a

Chun-Ho Liu; Mary C. Barth

2002-01-01

409

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

SciTech Connect

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

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

1990-05-01

410

Discovery of microdiamonds and associated minerals in the Makhtesh Ramon Canyon (Negev Desert, Israel)  

Microsoft Academic Search

The Makhtesh Ramon erosional?tectonic depression (canyon), 40 km long and approximately 8 km wide, is situated in the Negev Desert (southern Israel), 65 km southwest of the Dead Sea. The canyon rim and center are located at an altitude of 800?1000 and 400? 600 m, respectively. In terms of tectonics, this structure represents the southern margin of the Syrian-Sinai [1

L. V. Eppelbaum; V. L. Vaksman; S. V. Kuznetsov; L. V. Sazonova; S. A. Smirnov; A. V. Surkov; B. M. Bezlepkin; Yu. I. Katz; N. N. Korotaeva; G. I. Belovitskaya

2006-01-01

411

Lava Falls Rapid in Grand Canyon; effects of late Holocene debris flows on the Colorado River  

USGS Publications Warehouse

Lava Falls Rapid is the most formidable reach of whitewater on the Colorado River in Grand Canyon and is one of the most famous rapids in the world. Debris flows in 1939, 1954, 1955, 1966, and 1995, as well as prehistoric events, completely changed flow through the rapid. Floods cleared out much of the increased constrictions, but releases from Glen Canyon Dam, including the 1996 controlled flood, are now required to remove the boulders deposited by the debris flows.

Webb, Robert H.; Melis, Theodore S.; Griffiths, Peter G.; Elliott, John G.; Cerling, Thure E.; Poreda, Robert J.; Wise, Thomas W.; Pizzuto, James E.

1999-01-01

412

Elastomechanical methods in the exploration of the Valles Caldera, New Mexico. Final report, June 8, 1981-October 8, 1981  

SciTech Connect

The Valles caldera in the Jemez Mountains of New Mexico is a case of an active caldera that is an object for a comprehensive ground tilt field program to map both elastic and rheic discontinuities. Based on a rather comprehensive theoretical development that is outlined in five separate Essays, estimates of the amplitudes of some of the possible ground tilt signals were obtained. Based on the results, the strongest signals of the order of 100 to 200 nanoradians would appear to result from the purely elastic response of the caldera fill to a barometric forcing. Moreover, assuming a magmatic underplate below the Valles, barometric forcing may lead to a flexure of the upper crust that could generate tilt signals of a similar magnitude. Present data material is insufficient to allow a useful estimate to be made of the possible tilt signals due to the rheic properties of a Valles pluton that may be in the state of partial fusion.

Bodvarsson, G.

1981-01-01

413

Preliminary study of the potential environmental concerns associated with surface waters and geothermal development of the Valles Caldera  

SciTech Connect

A preliminary evaluation is presented of possible and probable problems that may be associated with hydrothermal development of the Valles Caldera Known Geothermal Resource Area (KGRA), with specific reference to surface waters. Because of the history of geothermal development and its associated environmental impacts, this preliminary evaluation indicates the Valles Caldera KGRA will be subject to these concerns. Although the exact nature and size of any problem that may occur is not predictable, the baseline data accumulated so far have delineated existing conditions in the streams of the Valles Caldera KGRA. Continued monitoring will be necessary with the development of geothermal resources. Further studies are also needed to establish guidelines for geothermal effluents and emissions.

Langhorst, G.J.

1980-06-01

414

Recent progress in CFD modelling of wind field and pollutant transport in street canyons  

NASA Astrophysics Data System (ADS)

With rapid development in computer hardware and numerical algorithms, computational fluid dynamics (CFD) techniques are widely utilized to study the wind field and pollutant transport in urban street canyons. The recent advancements and achievements in street-canyon pollution research using mathematical modelling approaches are reviewed in this paper. The standard, renormalized-group (RNG), and realizable k-? turbulence closure schemes are the most commonly used Reynolds-averaged Navier-Stokes (RANS) models in street-canyon flow research, including the studies on the effects of street-canyon aspect ratio, building configuration, ambient wind direction, inflow turbulence intensities, vehicle-induced turbulence, and thermal stratifications. Another approach to turbulence simulation inside street canyons is large-eddy simulation (LES) which can handle a broad range of turbulent motions in a transient manner. These two approaches have their merits and the choice between them will be a compromise between accuracy and cost. Several guidelines on this choice as well as some comments on the 2D and 3D CFD simulations are given. The outputs from wind field models can be used with pollutant transport models to calculate the pollutant distribution inside street canyons. The most commonly employed pollutant transport models include Lagrangian, Eulerian, and Lagrangian/Eulerian hybrid models. The advantages and shortcomings of these models are summarized. Several other modelling concerns, such as chemically reactive pollutant dispersion and boundary conditions treatment, are also discussed.

Li, Xian-Xiang; Liu, Chun-Ho; Leung, Dennis Y. C.; Lam, K. M.

415

Micrometeorological Measurements in a Street Canyon during the Joint ATREUS-PICADA Experiment  

NASA Astrophysics Data System (ADS)

In order to investigate the microclimatic conditions in a street canyon, a physical model was used to conduct the Joint ATREUS-PICADA Experiment (JAPEX) in situ experimental campaign. Four lines of buildings simulated by steel containers were installed to form three parallel street canyons at 1:5 scale, with width/height aspect ratio approximately 0.40. The reference wind and atmospheric conditions were measured, as well as the flow velocity and direction in the street. Preliminary results concern street canyon ventilation and thermal effects on in-canyon airflow, and show that vortical motions appear for reference wind directions perpendicular to the street axis. The presence of adjacent rows of buildings did not appear to significantly influence the flow character within the canyon for the case of a low aspect ratio corresponding to a skimming flow regime. The flow structure was not significantly affected by the thermal effects although some slight interference occurred in the lower part of the canyon. An analysis of horizontal temperature gradients indicated that a thin boundary layer develops near the heated facade. These facts imply that the thermal effects are considerable only very close to the wall.

Idczak, Marcin; Mestayer, Patrice; Rosant, Jean-Michel; Sini, Jean-Francois; Violleau, Michel

2007-07-01

416

Rapid Formation of a Modern Bedrock Canyon by a Single Flood Event (Invited)  

NASA Astrophysics Data System (ADS)

Although ancient megafloods have carved some of the most spectacular canyons on Earth and Mars, quantifying flood discharge, duration and erosion mechanics is hampered because we lack modern analogs. Canyon Lake Gorge, Texas, was carved in 2002 during a single catastrophic flood event and offers a rare opportunity to analyze canyon formation and test paleo-hydraulic-reconstruction techniques under known topographic and hydraulic conditions. Here we use topography and imagery from before and after the flood, discharge measured during the event, field measurements, and sediment-transport modeling to show that the flood moved meter-sized boulders, excavated ~7 m of rock, and transformed a soil-mantled valley into a bedrock canyon in ~ 3 days. Canyon morphology is strongly dependent on rock type where plucking of limestone blocks produced waterfalls, inner channels and strath terraces, and abrasion of cemented alluvium sculpted walls, plunge pools and streamlined islands. Canyon formation was so rapid that erosion might have been limited by the ability of the flow to transport sediment, which greatly simplifies modeling and may improve hydraulic reconstructions of other megafloods on Earth and Mars.

Lamb, M. P.; Fonstad, M. A.

2010-12-01

417

Crust and upper mantle P wave velocity structure beneath Valles Caldera, New Mexico: Results from the Jemez teleseismic tomography experiment  

NASA Astrophysics Data System (ADS)

New results are presented from the teleseismic component of the Jemez Tomography Experiment conducted across Valles caldera in northern New Mexico. We invert 4872 relative P wave arrival times recorded on 50 portable stations to determine velocity structure to depths of 40 km. The three principle features of our model for Valles caldera are: (1) near-surface low velocities of -17% beneath the Toledo embayment and the Valle Grande, (2) midcrustal low velocities of -23% in an ellipsoidal volume underneath the northwest quadrant of the caldera, and (3) a broad zone of low velocities (-15%) in the lower crust or upper mantle. Crust shallower than 20 km is generally fast to the northwest of the caldera and slow to the southeast. Near-surface low velocities are interpreted as thick deposits of Bandelier tuff and postcaldera volcaniclastic rocks. Lateral variation in the thickness of these deposits supports increased caldera collapse to the southeast, beneath the Valle Grande. We interpret the midcrustal low-velocity zone to contain a minimum melt fraction of 10%. While we cannot rule out the possibility that this zone is the remnant 1.2 Ma Bandelier magma chamber, the eruption history and geochemistry of the volcanic rocks erupted in Valles caldera following the Bandelier tuff make it more likely that magma results from a new pulse of intrusion, indicating that melt flux into the upper crust beneath Valles caldera continues. The low-velocity zone near the crust-mantle boundary is consistent with either partial melt in the lower crust or mafic rocks without partial melt in the upper mantle. In either case, this low-velocity anomaly indicates that underplating by mantle-derived melts has occurred.

Steck, Lee K.; Thurber, Clifford H.; Fehler, Michael C.; Lutter, William J.; Roberts, Peter M.; Baldridge, W. Scott; Stafford, Darrik G.; Sessions, Robert

1998-10-01

418

Caldera processes and magma-hydrothermal systems continental scientific drilling program: thermal regimes, Valles caldera research, scientific and management plan  

SciTech Connect

Long-range core-drilling operations and initial scientific investigations are described for four sites in the Valles caldera, New Mexico. The plan concentrates on the period 1986 to 1993 and has six primary objectives: (1) study the origin, evolution, physical/chemical dynamics of the vapor-dominated portion of the Valles geothermal system; (2) investigate the characteristics of caldera fill and mechanisms of caldera collapse and resurgence; (3) determine the physical/chemical conditions in the heat transfer zone between crystallizing plutons and the hydrothermal system; (4) study the mechanism of ore deposition in the caldera environment; (5) develop and test high-temperature drilling techniques and logging tools; and (6) evaluate the geothermal resource within a large silicic caldera. Core holes VC-2a (500 m) and VC-2b (2000 m) are planned in the Sulphur Springs area; these core holes will probe the vapor-dominated zone, the underlying hot-water-dominated zone, the boiling interface and probable ore deposition between the two zones, and the deep structure and stratigraphy along the western part of the Valles caldera fracture zone and resurgent dome. Core hole VC-3 will involve reopening existing well Baca number12 and deepening it from 3.2 km (present total depth) to 5.5 km, this core hole will penetrate the deep-crystallized silicic pluton, investigate conductive heat transfer in that zone, and study the evolution of the central resurgent dome. Core hole VC-4 is designed to penetrate deep into the presumably thick caldera fill in eastern Valles caldera and examine the relationship between caldera formation, sedimentation, tectonics, and volcanism. Core hole VC-5 is to test structure, stratigraphy, and magmatic evolution of pre-Valles caldera rocks, their relations to Valles caldera, and the influences of regional structure on volcanism and caldera formation.

Goff, F.; Nielson, D.L. (eds.)

1986-05-01

419

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

USGS Publications Warehouse

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

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

2012-01-01

420

A Structural Origin for the Warrego Rise, Thaumasia Highlands, Mars, and Implications for the Origin of Warrego Valles  

NASA Astrophysics Data System (ADS)

The Warrego Rise is a topographical high located in the Thaumasia Mountain Belt, Mars. Its southern slopes are incised by Warrego Valles, a valley network offered as an apparent “smoking gun” by those who ascribe dendritic channel networks to a warmer, wetter climate early in Mars history. Here, we investigate a new formation hypothesis for the Rise, and show that its structure and morphology are consistent with being a culmination caused by imbricate stacking. Such stacking can bring lenses of ice/salt up to high elevation, where fluids resulting from frictional heating or deep aquifers could travel along fractures to the surface, and flow down the Rise, dominantly incising Warrego Valles.

Som, S. M.; Montgomery, D. R.

2010-12-01

421

Structural characterization of the cerberus fossae and implications for paleodischarge of Athabasca Valles, Mars  

NASA Astrophysics Data System (ADS)

Mechanically interacting fault systems on Earth are often associated with groundwater flow (e.g. Curewitz and Karson, 1997) by facilitating water storage and flow through fracture conduits before, during, and after seismic events (e.g. Sibson, 1975). Similar associations between interacting fault segments and fluid flow are present on Mars (Davatzes and Gulick, 2007a). The Cerberus Fossae compose a system of elongate topographic lows, a portion of which coincides with the source region of the outflow channel Athabasca Valles. The Cerberus Fossae and source area were mapped using Thermal Emission Imaging System (THEMIS) daytime IR mosaics and Context camera (CTX) images to establish spatial relations of structural features. Mars Orbiter Laser Altimeter (MOLA) elevation data were plotted to construct the depth profiles of the fossae to test the hypothesis that the Cerberus Fossae are normal fault-bounded graben. High Resolution Imaging Science Experiment (HiRISE) images were mapped for fractures within the fault damage zones with the degree of fracture plotted as a function of distance along strike. This plot established the spatial relations between fractures, mechanically interacting fossae segments, and Athabasca Valles. The depth profiles of the Cerberus Fossae are consistent with the displacement distribution of terrestrial normal faults with a surface expression consistent with fault propagation from depth and mechanical interaction among segments. Similarly, regions of interpreted mechanical interaction indicated by slip distribution and segment overlap correspond to increased fracture intensity and density. On Earth, such regions of mechanical interaction tend to have high fracture intensity (e.g. Davatzes et al., 2005), are associated with hydrothermal fluid flow (Curewitz and Karson, 1997), and have evidence of extensive long-term fluid flow as evidenced by diagenetic alterations (Eichhubl et al., 2004). Higher fracture intensities and densities near the head of Athabasca Valles as a proxy for increased permeability provide a potential mechanism and a necessary condition for the localized fluid flux necessary to supply the outflow channel. Thus, I conclude the Cerberus Fossae are mechanically interacting normal fault-bounded graben with highly permeable damage zones that would act to quickly dewater an aquifer resulting in the carving of Athabasca Valles.

Runyon, Kirby D.

422

INCREASING OIL RECOVERY THROUGH ADVANCED REPROCESSING OF 3D SEISMIC, GRANT CANYON AND BACON FLAT FIELDS, NYE COUNTY, NEVADA  

Microsoft Academic Search

Makoil, Inc., of Orange, California, with the support of the U.S. Department of Energy has reprocessed and reinterpreted the 3D seismic survey of the Grant Canyon area, Railroad Valley, Nye County, Nevada. The project was supported by Dept. of Energy Grant DE-FG26-00BC15257. The Grant Canyon survey covers an area of 11 square miles, and includes Grant Canyon and Bacon Flat

Eric H. Johnson; Don E. French

2001-01-01

423

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

Microsoft Academic Search

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

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

2008-01-01

424

Numerical Simulation of Recent Turbidity Currents in the Monterey Canyon System, Offshore California  

NASA Astrophysics Data System (ADS)

The method of computational fluid dynamics (CFD) has been used, in the form of a 3D numerical model (Flow- 3D®), to perform a full-scale simulation of turbidity currents measured in December 2002 by three moorings in the Soquel and Monterey canyons. The model was verified by simulation of laboratory flows, and was upscaled to the Monterey Canyon system on the basis of high-resolution bathymetric data and flow measurements. The measured velocity profiles were sufficient to assess the flow thickness, initial velocity and duration in the canyon head zone. A computational grid with a highest feasible resolution was used, and both bathymetry and hydrostatic pressure were accounted for. The volumetric sediment concentration and exact grain- size composition of the flows were unknown, and thus a range of values for the initial concentration and bed roughness were assumed and assessed on a trial-and-error basis. The simulations reveal the behavior of a turbidity current along its descent path, including its local hydraulic characteristics (the 3D field of velocity, sediment concentration, shear stress, strain rate, and dynamic viscosity, as well as the magnitude of velocity and turbulent shear). The results confirm that the velocity structure of turbidity current is highly sensitive to variation in seafloor topography. The December 17th flow in the Soquel Canyon appears to have lost capacity by dilution over a relatively short distance and shown significant velocity fluctuations, which is attributed to the rugged topography of the canyon floor. A major loss of momentum occurred when the flow plunged at high angle into the Monterey Canyon, crashing against its bend's southern wall. The December 20th flow in the Monterey Canyon, in contrast, developed a considerably longer body and strongly accelerated towards the canyon's sharp second bend before crashing against its western wall. The mooring data show a down-canyon decline of velocity and suggest gradual waning, but the flow in reality appears to have had a new waxing phase. The CFD simulations allow the potential behavior of future flows to be predicted and, through a longer series of runs, the zones of erosion and deposition in the canyon system to be delineated.

Heimsund, S.; Xu, J.; Nemec, W.

2007-12-01

425

Evaluation of the thermal structure in an urban street canyon: field measurements and model simulation  

NASA Astrophysics Data System (ADS)

The results of a research project, aiming at providing tools and criteria to evaluate the temperature field inside an urban street canyon, are presented. Temperature measurements have been carried out, both in summertime and in wintertime, inside a North-South oriented urban canyon in the city of Trento (Italy) in the Alps, with sensors placed at various heights on the front of buildings flanking the street and on top of traffic lights in the middle of the canyon. The results have been analyzed in comparison with data from an automated weather station placed close to the street canyon, at 33 m above ground level and taken as a reference for the above roof-top level. During sunny days a well defined cycle was identified in the daily evolution of air temperature measured by the sensors inside the urban canyon, which was primarily influenced by direct solar radiation. As expected, during the morning the East-facing sensors warmed up faster than the other ones, while in the afternoon the West-facing instruments were the warmest. In most cases the air temperature inside the canyon was higher than above roof level, with differences depending on weather conditions and hour of the day. The dataset allowed to characterize the microclimate of the urban canopy layer and provided a basis for testing the ability of a simple numerical model to simulate the thermal structure inside the urban canyon. The model displays the following characteristics: assignment of distinct surface types (road, walls and roofs), in order to better simulate their physical properties; computation of radiative exchanges inside the canyon based on view factors between the different surfaces and explicitly treating both the solar reflections and the shadows; storage heat flux simulated by means of the heat conduction equation. The model requires as input the geometry parameters of the street and the values of meteorological variables measured above roof level. The main outputs are the heat fluxes determined by the surface energy balance (road, building fronts), the surface temperatures and the average air temperature inside the urban canyon. The comparison between the results of the model and the measurements made during the field experiments displays a good agreement, with an average error of 0.3-0.4 °C on the evaluation of the mean air temperature inside the street canyon. This result is remarkable, especially considering the low level of complexity of the numerical code and the simplifying assumptions made.

Giovannini, L.; de Franceschi, M.; Zardi, D.

2009-04-01

426

Environmental and human impact on the sedimentary dynamic in the Rhone Delta subaquatic canyons (France-Switzerland)  

NASA Astrophysics Data System (ADS)

Deltas are very sensitive environments and highly vulnerable to variations in water discharge and the amount of suspended sediment load provided by the delta-forming currents. Human activities in the watershed, such as building of dams and irrigation ditches, or river bed deviations, may affect the discharge regime and sediment input, thus affecting delta growth. Underwater currents create deeply incised canyons cutting into the delta lobes. Understanding the sedimentary processes in these subaquatic canyons is crucial to reconstruct the fluvial evolution and human impact on deltaic environments and to carry out a geological risk assessment related to mass movements, which may affect underwater structures and civil infractructure. Recently acquired high-resolution multibeam bathymetry on the Rhone Delta in Lake Geneva (Sastre et al. 2010) revealed the complexity of the underwater morphology formed by active and inactive canyons first described by Forel (1892). In order to unravel the sedimentary processes and sedimentary evolution in these canyons, 27 sediment cores were retrieved in the distal part of each canyon and in the canyon floor/levee complex of the active canyon. Geophysical, sedimentological, geochemical and radiometric dating techniques were applied to analyse these cores. Preliminary data show that only the canyon originating at the current river mouth is active nowadays, while the others remain inactive since engineering works in the watershed occurred, confirming Sastre et al. (2010). However, alternating hemipelagic and turbiditic deposits on the easternmost canyons, evidence underflow processes during the last decades as well. Two canyons, which are located close to the Rhone river mouth, correspond to particularly interesting deeply incised crevasse channels formed when the underwater current broke through the outer bend of a meander in the proximal northern levee. In these canyons, turbidites occur in the sediment record indicating ongoing sediment dynamics during whether extreme flood events or mass-movements due to deltaic scarp failures. The active canyon shows a classic turbiditic system with frequent spillover processes in the canyon floor/levee complex. Geotechnical measurements, a decrease in the frequency of turbidites and a fining upward sequence along the levee suggest that erosion dominates sedimentation in the canyon floor, while sedimentation dominates in the rapid levee building-up process, with sedimentation rates that exceed 3cm/yr in the proximal areas. Therefore, mechanisms controlling the sedimentary evolution on the active canyon result in a complex interplay between erosion and sedimentation. Further research will provide a detailed evaluation of the human impact on sedimentary dynamic in the Rhone Delta subaquatic canyons.

Arantegui, A.; Corella, J. P.; Loizeau, J. L.; Anselmetti, F. S.; Girardclos, S.

2012-04-01

427

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

428

The effects of wildfire on the peak streamflow magnitude and frequency, Frijoles and Capulin Canyons, Bandelier National Monument, New Mexico  

USGS Publications Warehouse

In June of 1977, the La Mesa fire burned 15,270 acres in and around Frijoles Canyon, Bandelier National Monument and the adjacent Santa Fe National Forest, New Mexico. The Dome fire occurred in April of 1996 in Bandelier National Monument, burned 16,516 acres in Capulin Canyon and the surrounding Dome Wilderness area. Both canyons are characterized by extensive archeological artifacts, which could be threatened by increased runoff and accelerated rates of erosion after a wildfire. The U.S. Geological Survey (USGS) in cooperation with the National Park Service monitored the fires' effects on streamflow in both canyons. Copyright 2004 ASCE.

Veenhuis, J. E.

2004-01-01

429

Determinacion de elementos en la atmosfera del Valle de Toluca por Activacion Neutronica (Julio 1992 - Abril 1993). (Determination of elements in the atmosphere of Valle de Toluca by Neutron Activation (July 1992 - April 1993)).  

National Technical Information Service (NTIS)

The purpose of this study is to continue with the environmental monitoring program of Valle de Toluca by means of the Neutron Activation Analysis and atomic absorption techniques. The analytical results corresponding to the period of July 1992 to April 19...

I. Garcia

1994-01-01

430

Effects of the Post-Glen Canyon Dam Flow Regime on the Old High Water Line Plant Community Along the Colorado River in Grand Canyon.  

National Technical Information Service (NTIS)

Growth and reproduction of native riparian trees were studied along the Colorado River in Grand Canyon. Populations of mesquite and acacia in the old high water zone were found to be growing and reproducing successfully. Shoot growth in adults is not sign...

L. S. Anderson G. A. Ruffner

1987-01-01

431

Restoring Anadromous Fish Habitat in Big Canyon Creek Watershed; Anadromous Fish Habitat Restoration in the Nichols Canyon Subwatershed, 2000 Annual Report  

Microsoft Academic Search

Nez Perce Soil & Water Conservation District (NPSWCD) undertook the Nichols Canyon Subwatershed Steelhead Trout Habitat Improvement Project in the spring of 1999 with funding from a grant through the Bonneville Power Administration. The Project's purpose is to install and implement agricultural best management practices (MBPS) and riparian restorations with the goal of improving steelhead trout spawning and rearing habitat

Koziol; Deb

2001-01-01

432

Restoring Anadromous Fish Habitat in Big Canyon Creek Watershed; Anadromous Fish Habitat Restoration in the Nichols Canyon Subwatershed, 2001 Annual Report  

Microsoft Academic Search

Big Canyon Creek historically provided quality spawning and rearing habitat for A-run wild summer steelhead in the Clearwater River subbasin (Fuller, 1986). However, high stream temperatures, excessive sediment and nutrient loads, low summer stream flows, and little instream cover caused anadromous fish habitat constraints in the creek. The primary sources of these nonpoint source pollution and habitat degradations are attributed

Koziol; Deb

2002-01-01

433

Restoring Anadromous Fish Habitat in Big Canyon Creek Watershed; Anadromous Fish Habitat Restoration in the Nichols Canyon Subwatershed, 1999 Annual Report  

Microsoft Academic Search

Nez Perce Soil & Water Conservation District (NPSWCD) undertook the Nichols Canyon Subwatershed Steelhead Trout Habitat Improvement Project in the spring of 1999. This Project is funded through a grant provided by the Bonneville Power Administration. The Project's purpose is to install and implement agricultural best management practices (BMPs) and riparian restorations to improve steelhead trout spawning and rearing habitat

Koziol; Deb

2000-01-01

434

Wind and topographic effects on the Labrador Current at Carson Canyon  

NASA Astrophysics Data System (ADS)

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

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

1987-09-01

435

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

NASA Astrophysics Data System (ADS)

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

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

2008-12-01

436

Large-eddy simulation of turbulent flow in a street canyon  

NASA Astrophysics Data System (ADS)

The turbulent flow inside an idealized urban street canyon with an aspect ratio of one is studied by means of large-eddy simulation. The Regional Atmospheric Modelling System is configured to simulate the turbulent flow in a neutrally stratified atmosphere with the initial wind perpendicular to the street canyon axis. The mean velocity components, resolved-scale turbulent kinetic energy (RS-TKE), the skewness and kurtosis of the resolved-scale velocity components (u along the canyon and w vertically) are compared with wind-tunnel measurements. The comparison indicates that a reasonable agreement is achieved. The simulation slightly underestimates the intensity of the primary eddy. It is found that distribution of the RS-TKE is very asymmetric: high in the vicinity of the downstream wall, and uniformly low in the vicinity of the upstream wall. The analyses of skewness and kurtosis indicate that there is a layer just below the rooftop in the canyon where ejection events dominate. Quadrant analysis of resolved-scale velocity fluctuations, u and w, under the rooftop at the centre of the canyon reveals that the exchange of momentum across the canyon top is contributed unevenly by different events. Weak ejection events dominate the frequency of occurrences, but fewer strong sweep events contribute the majority of the total momentum transfer. The features of momentum transfer are further investigated by analysing the spatial-temporal variations of u, w, and uw at the roof level. It is found that the variation of these variables is highly intermittent and is associated with multi-scale turbulent events. The period of eddies containing high RS-TKE is attributed to the Kelvin-Helmhotz instabilities. These results improve our understanding of the turbulent structure in street canyon flow.

Cui, Zhiqiang; Cai, Xiaoming; Baker, J. Chris

2004-04-01

437

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

NASA Astrophysics Data System (ADS)

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

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

2009-01-01

438

Canyon drainage induced mixing over a large basin  

SciTech Connect

Complex terrain surrounding urbanized basins around the world has long been recognized to strongly affect the characteristics of vertical transport and mixing of pollutants. The Department of Energy's Vertical Transport and Mixing (VTMX) program will investigate mixing processes within night-time boundary layers over large urban basins. The program will launch several field experiments within the Salt Lake City basin in the coming years. This modeling study, like many other studies being undertaken by the participants of the VTMX programs, is intended to complement the proposed field experiments by numerically examining some of the flow interactions known to occur in large basins. Using idealized simulations, we particularly investigate drainage flows from deep canyons similar to those along the Wasatch Front into the Salt Lake City basin. Literature shows that under favorable conditions, drainage flows can generate bore waves that may propagate ahead of the density current (e.g., Simpson 1969; Simpson 1982; Crook and Miller 1985). Existence and frequency of such bore waves can profoundly influence the spatial and temporal variability of vertical transport and mixing within large basins. If bore waves do occur on a regular basis within the Salt Lake City basin (a task for the upcoming experiments to determine), then understanding the basin-scale conditions under which these waves are produced and how they may propagate and interact with the city's buildings will be of great importance in characterizing transport and mixing processes within the basin.

Stalker, J. [and others

2000-05-01

439

Wintertime surface energy budget variations in the Grand Canyon region  

SciTech Connect

Few detailed technical studies of the spatial variation of long and shortwave radiation or individual components of the surface energy budget have yet been conducted in areas of com