Sample records for academician ridge lake

  1. Tsunami-generated boulder ridges in Lake Tahoe, California-Nevada

    USGS Publications Warehouse

    Moore, J.G.; Schweickert, R.A.; Robinson, J.E.; Lahren, M.M.; Kitts, Christopher A.

    2006-01-01

    An array of east-trending ridges 1-2 m high and up to 2 km long occurs on the Tahoe City shelf, a submerged wave-cut bench <15 m deep in the northwest sector of the lake. The shelf is just north of the amphitheater of the giant subaqueous 10 km3 McKinney Bay landslide, which originated on the west wall of Lake Tahoe. Images from a submersible camera show that the ridges are composed of loose piles of boulders and cobbles that lie directly on poorly consolidated, fine-bedded lake beds deposited in an ancestral Lake Tahoe. Dredge hauls from landslide distal blocks, as well as from the walls of the re-entrant of the landslide, recovered similar lake sediments. The McKinney Bay landslide generated strong currents, which rearranged previous glacial-derived debris into giant ripples creating the boulder ridges. The uncollapsed part of the sediment bench, including the Tahoe City shelf, poses a hazard because it may fail again, producing a landslide and damaging waves. ?? 2006 Geological Society of America.

  2. INSECT SPECIES ON VEGETATION OF THE WHITE OAK LAKE BED, OAK RIDGE, TENNESSEE

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Howden, H.F.; Crossley, D.A. Jr.

    White Oak Lake, Oak Ridge, Tennessee, received lowlevel radioactive wastes from Oak Ridge National Laboratory for 12 years prior to draining in 1955. Studies on the insects inhabiting the vegetation on White Oak Lake bed revealed 401 species present during 1956 and 1957. Most numerous were members of the insect Orders Hymenoptera, Diptera, and Coleoptera. In the summer of 1956, the first summer following draining of the lake, there were relatively fewer species of insects represented by large numbers of individuals. In 1957, there were relatively more species of insects but fewer individuals were present. By the end of themore » summer of 1957, only two years after the lake was drained, the vegetation supported a rich and varied insect fauna. (C.H.)« less

  3. A synthesis of post-glacial diatom records from Lake Baikal

    USGS Publications Warehouse

    Bradbury, J. Platt; Bezrukova, E.; Chernyaeva, G.; Colman, S.M.; Khursevich, G.; King, J.W.; Likoshway, Ye. V.

    1994-01-01

    The biostratigraphy of fossil diatoms contributes important chronologic, paleolimnologic, and paleoclimatic information from Lake Baikal in southeastern Siberia. Diatoms are the dominant and best preserved microfossils in the sediments, and distinctive assemblages and species provide inter-core correlations throughout the basin at millennial to centennial scales, in both high and low sedimentation-rate environments. Distributions of unique species, once dated by radiocarbon, allow diatoms to be used as dating tools for the Holocene history of the lake.Diatom, pollen, and organic geochemical records from site 305, at the foot of the Selenga Delta, provide a history of paleolimnologic and paleoclimatic changes from the late glacial (15 ka) through the Holocene. Before 14 ka diatoms were very rare, probably because excessive turbidity from glacial meltwater entering the lake impeded productivity. Between 14 and 12 ka, lake productivity increased, perhaps as strong winds promoted deep mixing and nutrient regeneration. Pollen evidence suggests a cold shrub — steppe landscape dominated the central Baikal depression at this time. As summer insolation increased, conifers replaced steppe taxa, but diatom productivity declined between 11 and 9 ka perhaps as a result of increased summer turbidity resulting from violent storm runoff entering the lake via short, steep drainages. After 8 ka, drier, but more continental climates prevailed, and the modern diatom flora of Lake Baikal came to prominence.On Academician Ridge, a site of slow sedimentation rates, Holocene diatom assemblages at the top of 10-m cores reappear at deeper levels suggesting that such cores record at least two previous interglacial (or interstadial?) periods. Nevertheless, distinctive species that developed prior to the last glacial period indicate that the dynamics of nutrient cycling in Baikal and the responsible regional climatic environments were not entirely analogous to Holocene conditions. During

  4. Water Quality and Evaluation of Pesticides in Lakes in the Ridge Citrus Region of Central Florida

    USGS Publications Warehouse

    Choquette, Anne F.; Kroening, Sharon E.

    2009-01-01

    Water chemistry, including major inorganic constituents, nutrients, and pesticide compounds, was compared between seven lakes surrounded by citrus agriculture and an undeveloped lake on the Lake Wales Ridge (herein referred to as the Ridge) in central Florida. The region has been recognized for its vulnerability to the leaching of agricultural chemicals into the subsurface due to factors including soils, climate, and land use. About 40 percent of Florida's citrus cultivation occurs in 'ridge citrus' areas characterized by sandy well drained soils, with the remainder in 'flatwoods citrus' characterized by high water tables and poorly drained soils. The lakes on the Ridge are typically flow-through lakes that exchange water with adjacent and underlying aquifer systems. This study is the first to evaluate the occurrence of pesticides in lakes on the Ridge, and also represents one of the first monitoring efforts nationally to focus on regional-scale assessment of current-use pesticides in small- to moderate-sized lakes (5 to 393 acres). The samples were collected between December 2003 and September 2005. The lakes in citrus areas contained elevated concentrations of major inorganic constituents (including alkalinity, total dissolved solids, calcium, magnesium, sodium, potassium, chloride, and sulfate), total nitrogen, pH, and pesticides compared to the undeveloped lake. Nitrate (as N) and total nitrogen concentrations were typically elevated in the citrus lakes, with maximum values of 4.70 and 5.19 mg/L (milligrams per liter), respectively. Elevated concentrations of potassium, nitrate, and other inorganic constituents in the citrus lakes likely reflect inputs from the surficial ground-water system that originated predominantly from agricultural fertilizers, soil amendments, and inorganic pesticides. A total of 20 pesticide compounds were detected in the lakes, of which 12 compounds exceeded the standardized reporting level of 0.06 ug/L (microgram per liter). Those

  5. Sublake geologic structure from high-resolution seismic-reflection data from four sinkhole lakes in the Lake Wales Ridge, Central Florida

    USGS Publications Warehouse

    Tihansky, A.B.; Arthur, J.D.; DeWitt, D.W.

    1996-01-01

    Seismic-reflection profiles from Lake Wales, Blue Lake, Lake Letta, and Lake Apthorp located along the Lake Wales Ridge in central Florida provide local detail within the regional hydrogeologic framework as described by litho- and hydrostratigraphic cross sections. Lakes located with the mantled karst region have long been considered to be sinkhole lakes, originating from subsidence activity. High-resolution seismic- reflection data confirm this origin for these four lakes. The geologic framework of the Lake Wales Ridge has proven to be a suitable geologic setting for continuous high-resolution seismic-reflection profiling in lakes; however, the nature of the lake-bottom sediments largely controls the quality of the seismic data. In lakes with significant organic-rich bottom deposits, interpretable record was limited to areas where organic deposits were minimal. In lakes with clean, sandy bottoms, the seismic-reflection methods were highly successful in obtaining data that can be correlated with sublake subsidence features. These techniques are useful in examining sublake geology and providing a better understanding of how confining units are affected by subsidence in a region where their continuity is of significant importance to local lake hydrology. Although local geologic control around each lake generally corresponds to the regional geologic framework, local deviations from regional geologic trends occur in sublake areas affected by subsidence activity. Each of the four lakes examined represents a unique set of geologic controls and provides some degree of structural evidence of subsidence activity. Sublake geologic structures identified include: (1) marginal lake sediments dipping into bathymetric lows, (2) lateral discontinuity of confining units including sags and breaches, (3) the disruption and reworking of overlying unconsolidated siliciclastic sediments as they subside into the underlying irregular limestone surface, and (4) sublake regions where

  6. Strand-plain evidence for late Holocene lake-level variations in Lake Michigan

    USGS Publications Warehouse

    Thompson, T.A.; Baedke, S.J.

    1997-01-01

    Lake level is a primary control on shoreline behavior in Lake Michigan. The historical record from lake-level gauges is the most accurate source of information on past lake levels, but the short duration of the record does not permit the recognition of long-term patterns of lake-level change (longer than a decade or two). To extend the record of lake-level change, the internal architecture and timing of development of five strand plains of late Holocene beach ridges along the Lake Michigan coastline were studied. Relative lake-level curves for each site were constructed by determining the elevation of foreshore (swash zone) sediments in the beach ridges and by dating basal wetland sediments in the swales between ridges. These curves detect long-term (30+ yr) lake-level variations and differential isostatic adjustments over the past 4700 yr at a greater resolution than achieved by other studies. The average timing of beach-ridge development for all sites is between 29 and 38 yr/ridge. This correspondence occurs in spite of the embayments containing the strand plains being different in size, orientation, hydrographic regime, and available sediment type and caliber. If not coincidental, all sites responded to a lake-level fluctuation of a little more than three decades in duration and a range of 0.5 to 0.6 m. Most pronounced in the relative lake-level curves is a fluctuation of 120-180 yr in duration. This ???150 yr variation is defined by groups of four to six ridges that show a rise and fall in foreshore elevations of 0.5 to 1.5 m within the group. The 150 yr variation can be correlated between sites in the Lake Michigan basin. The ???30 and 150 yr fluctuations are superimposed on a long-term loss of water to the Lake Michigan basin and differential rates of isostatic adjustment.

  7. Phosphate mineral formation in Lake Baikal sediments and implications for paleoclimate

    NASA Astrophysics Data System (ADS)

    Fagel, N.; Alleman, L. Y.; André, L.; Cloots, R.; Hatert, F.; Juvigné, E.; Renson, V.

    2003-04-01

    The more than 20 million years old Lake Baikal sedimentary record provides a good climate archive. While most paleoclimate reconstructions are mainly based on biotic proxies, we tested in this study other minerogenic tracers. In particular, it was suggested that the formation of authigenic and/or diagenetic phosphate minerals in Baïkal sediments underlines transitions from glacial to interglacial periods (Deike et al., 1997). The phosphate mineral formation previously evidenced (Müller et al., 2002) may be sensitive to suspended sediment concentrations: glacial periods are characterised by high detrital discharge, interglacial intervals are marked by low detrital supply but high biogenic sedimentation. Phosphate minerals were observed in Baïkal sediments from recent to 65 kyr BP. Their abundance was related to the sedimentation rate, the phosphate enrichment layers being particularly common on low sedimentation site, i.e., the Academician Ridge. Major and trace elements have been analysed by ICP-AES and ICP-MS on four cores drilled on topographic hills, in the southern basin (Posolsky bank, CON01-604), in the central part (Academician Ridge, VER98-1-3 and VER98-1-14) and in the northern basin (Continent Ridge, CON01-603). The geochemical signature is consistent with the occurrence of Mn-Fe-phosphate minerals. For instance P2O5 reaches up to 3% wt. relative to a mean value of 0.3 in the background sediment, MnO2 presents an enrichment factor up to 6. There is no associated enrichment in any of the trace elements measured at the same levels. In the sediments, those P-Mn-Fe rich levels are related either to sparse millimetric dark concretions or to a layer (or a group of layers) defined by an alignment of numerous concretions but there is no so-called crusts. The concretions, isolated by >63 mm sieving, present a lamellar morphology. They are identified as Fe-phosphate phases with a variable proportion of Mn. The powder diffraction diagram is consistent with

  8. Quaternary sedimentation and subsidence history of Lake Baikal, Siberia, based on seismic stratigraphy and coring

    USGS Publications Warehouse

    Colman, Steven M.; Karabanov, E.B.; Nelson, C. H.

    2003-01-01

    The long, continuous, high-latitude, stratigraphic record of Lake Baikal was deposited in three broad sedimentary environments, defined by high-resolution seismic-reflection and coring methods: (1) turbidite depositional systems, by far the most widespread, characterizing most of the margins and floors of the main basins of the lake, (2) large deltas of major drainages, and (3) tectonically or topographically isolated ridges and banks. Holocene sedimentation rates based on radiocarbon ages vary by more than an order of magnitude among these environments, from less than about 0.03 mm/yr on ridges and banks to more than about 0.3 mm/yr on basin floors. Extrapolating these rates, with a correction for compaction, yields tentative estimates of about 25 and 11 Ma for the inception of rifting in the Central and North basins, respectively, and less than 6 Ma for the 200-m sediment depth on Academician Ridge. The Selenga Delta has the distinctive form of a classic prograding Gilbert-type delta, but its history appears to represent a complex combination of tectonism and sedimentation. The central part of the delta is underlain by prograding, shallow-water sequences, now several hundred meters below the lake surface. These deposits and much of the delta slope are mantled by fine-grained, deep-water, hemipelagic deposits whose base is estimated to be about 650,000 years old. Modern coarse-grained sediment bypasses the delta slope through fault-controlled canyons that feed large, subaqueous fans at the ends of the South and Central basins. These relations, along with abundant other evidence of recent faulting and the great depths of the Central and South basins, suggest that these two rift basins have experienced a period of unusually rapid subsidence over the last 650,000 years, during at least part of which sedimentation has failed to keep pace.

  9. AMS radiocarbon analyses from Lake Baikal, Siberia: Challenges of dating sediments from a large, oligotrophic lake

    USGS Publications Warehouse

    Colman, Steven M.; Jones, Glenn A.; Rubin, M.; King, J.W.; Peck, J.A.; Orem, W.H.

    1996-01-01

    A suite of 146 new accelerator-mass spectrometer (AMS) radiocarbon ages provides the first reliable chronology for late Quaternary sediments in Lake Baikal. In this large, highly oligotrophic lake, biogenic and authigenic carbonate are absent, and plant macrofossils are extremely rare. Total organic carbon is therefore the primary material available for dating. Several problems are associated with the TOC ages. One is the mixture of carbon sources in TOC, not all of which are syndepositional in age. This problem manifests itself in apparent ages for the sediment surface that are greater than zero. However, because most of the organic carbon in Lake Baikal sediments is algal (autochthonous) in origin, this effect is limited to about 1000+500 years, which can be corrected, at least for young deposits. The other major problem with dating Lake Baikal sediments is the very low carbon contents of glacial-age deposits, which makes them extremely susceptible to contamination with modern carbon. This problem can be minimized by careful sampling and handling procedures. The ages show almost an order of magnitude difference in sediment-accumulation rates among different sedimentary environments in Lake Baikal, from about 0.04 mm/year on isolated banks such as Academician Ridge, to nearly 0.3 mm/year in the turbidite depositional areas beneath the deep basin floors, such as the Central Basin. The new AMS ages clearly indicate that the dramatic increase in diatom productivity in the lake, as evidenced by increases in biogenic silica and organic carbon, began about 13 ka, in contrast to previous estimates of 7 ka for the age of this transition. Holocene net sedimentation rates may be less than, equal to, or greater than those in the late Pleistocene, depending on the site. This variability reflects the balance between variable terrigenous sedimentation and increased biogenic sedimentation during interglaciations. The ages reported here, and the temporal and spatial variation in

  10. Difficulties Encountered by Academicians in Academic Research Processes in Universities

    ERIC Educational Resources Information Center

    Yalçin, Sinan; Altun Yalçin, Sema

    2017-01-01

    This present research, aimed to determine the occasions, which the academicians encountered during the academic research process and how these affect the research process, was prepared as a case study pattern among the qualitative research methods. 34 academicians, who were working in a university in Turkey, participated in the research. The data…

  11. Career Experiences of Women Academicians in Kenyan Institutions of Higher Learning

    ERIC Educational Resources Information Center

    Nanyama, Evalyne

    2012-01-01

    Currently, women academicians in Kenya are underrepresented at all levels in Kenyan IHL, leading to less participation and integration into the administration and governance of higher institutions. As a result women academicians have little chance of making meaningful contributions to important policies and decisions that affect the institutions…

  12. Evaluation of Workload and its Impact on Satisfaction Among Pharmacy Academicians in Southern India.

    PubMed

    Ahmad, Akram; Khan, Muhammad Umair; Srikanth, Akshaya B; Patel, Isha; Nagappa, Anantha Naik; Jamshed, Shazia Qasim

    2015-06-01

    The purpose of this study was to determine the level of workload among pharmacy academicians working in public and private sector universities in India. The study also aimed to assess the satisfaction of academicians towards their workload. A cross-sectional study was conducted for a period of 2 months among pharmacy academicians in Karnataka state of Southern India. Convenience sampling was used to select a sample and was contacted via email and/or social networking sites. Questionnaire designed by thorough review literature was used as a tool to collect data on workload (teaching, research, extracurricular services) and satisfaction. Of 214 participants, 95 returned the filled questionnaire giving the response rate of 44.39%. Private sector academicians had more load of teaching (p=0.046) and they appeared to be less involved in research activities (p=0.046) as compared to public sector academicians. More than half of the respondents (57.9%) were satisfied with their workload with Assistant Professors were least satisfied as compared to Professors (p=0.01). Overall, private sector academicians are more burdened by teaching load and also are less satisfied of their workload. Revision of private universities policies may aid in addressing this issue.

  13. 36 CFR 7.34 - Blue Ridge Parkway.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 36 Parks, Forests, and Public Property 1 2013-07-01 2013-07-01 false Blue Ridge Parkway. 7.34... REGULATIONS, AREAS OF THE NATIONAL PARK SYSTEM § 7.34 Blue Ridge Parkway. (a) Snowmobiles. After consideration... waters of the Blue Ridge Parkway is prohibited except on the waters of Price Lake. (2) Vessels using...

  14. 36 CFR 7.34 - Blue Ridge Parkway.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 36 Parks, Forests, and Public Property 1 2014-07-01 2014-07-01 false Blue Ridge Parkway. 7.34... REGULATIONS, AREAS OF THE NATIONAL PARK SYSTEM § 7.34 Blue Ridge Parkway. (a) Snowmobiles. After consideration... waters of the Blue Ridge Parkway is prohibited except on the waters of Price Lake. (2) Vessels using...

  15. 36 CFR 7.34 - Blue Ridge Parkway.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 36 Parks, Forests, and Public Property 1 2012-07-01 2012-07-01 false Blue Ridge Parkway. 7.34... REGULATIONS, AREAS OF THE NATIONAL PARK SYSTEM § 7.34 Blue Ridge Parkway. (a) Snowmobiles. After consideration... waters of the Blue Ridge Parkway is prohibited except on the waters of Price Lake. (2) Vessels using...

  16. Academicians' Career Capital and Career Satisfaction: The Mediation Effect of Research Productivity

    ERIC Educational Resources Information Center

    Aytekin, Ihsan; Erdogmus, Nihat; Erdil, Oya; Akgün, Ali E.

    2016-01-01

    The competitive advantages of knowledge-producing institutions are their wise, creative, enthusiastic, and excited academicians and their competences. Currently, questions come to the fore as to which variables affect the research performance of university-employed academicians, and what role does research performance have in the relationship of…

  17. 42. Peaks of Otter, Abbott Lake. View across lake to ...

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

    42. Peaks of Otter, Abbott Lake. View across lake to peaks of Outter Lodge, completed in 1964. Construction of the lake got underway in 1964. Looking east-northeast. - Blue Ridge Parkway, Between Shenandoah National Park & Great Smoky Mountains, Asheville, Buncombe County, NC

  18. Evaluation of Workload and its Impact on Satisfaction Among Pharmacy Academicians in Southern India

    PubMed Central

    Khan, Muhammad Umair; Srikanth, Akshaya B.; Patel, Isha; Nagappa, Anantha Naik; Jamshed, Shazia Qasim

    2015-01-01

    Objective The purpose of this study was to determine the level of workload among pharmacy academicians working in public and private sector universities in India. The study also aimed to assess the satisfaction of academicians towards their workload. Materials and Methods A cross-sectional study was conducted for a period of 2 months among pharmacy academicians in Karnataka state of Southern India. Convenience sampling was used to select a sample and was contacted via email and/or social networking sites. Questionnaire designed by thorough review literature was used as a tool to collect data on workload (teaching, research, extracurricular services) and satisfaction. Results Of 214 participants, 95 returned the filled questionnaire giving the response rate of 44.39%. Private sector academicians had more load of teaching (p=0.046) and they appeared to be less involved in research activities (p=0.046) as compared to public sector academicians. More than half of the respondents (57.9%) were satisfied with their workload with Assistant Professors were least satisfied as compared to Professors (p=0.01). Conclusion Overall, private sector academicians are more burdened by teaching load and also are less satisfied of their workload. Revision of private universities policies may aid in addressing this issue. PMID:26266133

  19. Mid Holocene lake level and shoreline behavior during the Nipissing phase of the upper Great Lakes at Alpena, Michigan, USA

    USGS Publications Warehouse

    Thompson, T.A.; Lepper, K.; Endres, A.L.; Johnston, J.W.; Baedke, S.J.; Argyilan, E.P.; Booth, R.K.; Wilcox, D.A.

    2011-01-01

    The Nipissing phase was the last pre-modern high-water stage of the upper Great Lakes. Represented as either a one- or two-peak highstand, the Nipissing occurred following a long-term lake-level rise. This transgression was primarily an erosional event with only the final stage of the transgression preserved as barriers, spits, and strandplains of beach ridges. South of Alpena, Michigan, mid to late Holocene coastal deposits occur as a strandplain between Devils Lake and Lake Huron. The landward part of this strandplain is a higher elevation platform that formed during the final stage of lake-level rise to the Nipissing peak. The pre-Nipissing shoreline transgressed over Devils Lake lagoonal deposits from 6.4 to 6.1. ka. The first beach ridge formed ~ 6. ka, and then the shoreline advanced toward Lake Huron, producing beach ridges about every 70. years. This depositional regression produced a slightly thickening wedge of sediment during a lake-level rise that formed 20 beach ridges. The rise ended at 4.5. ka at the Nipissing peak. This peak was short-lived, as lake level fell > 4. m during the following 500. years. During this lake-level rise and subsequent fall, the shoreline underwent several forms of shoreline behavior, including erosional transgression, aggradation, depositional transgression, depositional regression, and forced regression. Other upper Great Lakes Nipissing platforms indicate that the lake-level change observed at Alpena of a rapid pre-Nipissing lake-level rise followed by a slower rise to the Nipissing peak, and a post-Nipissing rapid lake-level fall is representative of mid Holocene lake level in the upper Great Lakes. ?? 2011 Elsevier B.V.

  20. Estimating ground-water exchange with lakes using water-budget and chemical mass-balance approaches for ten lakes in ridge areas of Polk and Highlands counties, Florida

    USGS Publications Warehouse

    Sacks, L.A.; Swancar, Amy; Lee, T.M.

    1998-01-01

    Water budget and chemical mass-balance approaches were used to estimate ground-water exchange with 10 lakes in ridge areas of Polk and Highlands Counties, Florida. At each lake, heads were monitored in the surficial aquifer system and deeper Upper Floridan aquifer, lake stage and rainfall were measured continuously, and lakes and wells were sampled three times between October 1995 and December 1996. The water-budget approach computes net ground-water flow (ground-water inflow minus outflow) as the residual of the monthly waterbudget equation. Net ground-water flow varied seasonally at each of the 10 lakes, and was notably different between lakes, illustrating short-term differences in ground-water fluxes. Monthly patterns in net ground-water flow were related to monthly patterns of other hydrologic variables such as rainfall, ground-water flow patterns, and head differences between the lake and the Upper Floridan aquifer. The chemical mass-balance approach combines the water budget and solute or isotope mass-balance equations, and assumes steady-state conditions. Naturally occurring tracers that were analyzed for include calcium, magnesium, sodium, potassium, chloride, and bromide, the isotopes deuterium and oxygen-18. Chloride and sodium were the most successful solute tracers; however, their concentrations in ground water typically varied spatially, and in places were similar to that in lake water, limiting their sensitivity as tracers. In contrast, the isotopes were more robust tracers because the isotopic composition of ground water was relatively uniform and was distinctly different from the lake water. Groundwater inflow computed using the chemical massbalance method varied significantly between lakes, and ranged from less than 10 to more than 150 inches per year. Both water-budget and chemical mass-balance approaches had limitations, but the multiple lines of evidence gained using both approaches improved the understanding of the role of ground water in the

  1. A rock-magnetic record from Lake Baikal, Siberia: Evidence for Late Quaternary climate change

    USGS Publications Warehouse

    Peck, J.A.; King, J.W.; Colman, Steven M.; Kravchinsky, V.A.

    1994-01-01

    Rock-magnetic measurements of sediment cores from the Academician Ridge region of Lake Baikal, Siberia show variations related to Late Quaternary climate change. Based upon the well-dated last glacial-interglacial transition, variations in magnetic concentration and mineralogy are related to glacial-interglacial cycles using a conceptual model. Interglacial intervals are characterized by low magnetic concentrations and a composition that is dominated by low coercivity minerals. Glacial intervals are characterized by high magnetic concentrations and increased amounts of high coercivity minerals. The variation in magnetic concentration is consistent with dilution by diatom opal during the more productive interglacial periods. We also infer an increased contribution of eolian sediment during the colder, windier, and more arid glacial conditions when extensive loess deposits were formed throughout Europe and Asia. Eolian transport is inferred to deliver increased amounts of high coercivity minerals as staining on eolian grains during the glacial intervals. Variations in magnetic concentration and mineralogy of Lake Baikal sediment correlate to the SPECMAP marine oxygen-isotope record. The high degree of correlation between Baikal magnetic concentration/mineralogy and the SPECMAP oxygen-isotope record indicates that Lake Baikal sediment preserves a history of climate change in central Asia for the last 250 ka. This correlation provides a method of estimating the age of sediment beyond the range of the radiocarbon method. Future work must include providing better age control and additional climate proxy data, thereby strengthening the correlation of continental and marine climate records. ?? 1994.

  2. The Early Tech Development Course: Experiential Commercialization Education for the Medical Academician.

    PubMed

    Servoss, Jonathan; Chang, Connie; Fay, Jonathan; Ward, Kevin

    2017-04-01

    Research produced by medical academicians holds promise for developing into biomedical innovations in therapeutics, devices, diagnostics, and health care information technology; however, the road to biomedical innovation is fraught with risk, including the challenge of moving from basic research insight onto a viable commercialization path. Compounding this challenge is the growing demand on medical academicians to be more productive in their clinical, teaching, and research duties within a resource-constrained environment. In 2014, the University of Michigan (UM) Medical School and College of Engineering codesigned and implemented an accelerated, biomedical-focused version of the National Science Foundation (NSF) Innovation Corps (I-Corps) program. The UM Early Tech Development (ETD) Course, designed for medical academicians exploring the commercial potential of early-stage ideas, covers the NSF I-Corps concept; supports the formation of teams of faculty, graduate, and medical students; and accommodates medical academicians' schedules. From 2014 to 2015, the ETD Course graduated 39 project teams from UM and other institutions. One-third of the teams have continued to pursue their projects, receiving additional funding, engaging industry partners, or enrolling in the NSF I-Corps program. The ETD Course, a potential pipeline to the NSF I-Corps program, captures a target audience of medical academicians and others in academic medicine. To better understand the long-term effects of the course and its relationship to the NSF I-Corps program, the authors will conduct a study on the careers of all ETD Course graduates, including those who have enrolled in NSF I-Corps versus those who have not.

  3. The Relationship between General Self-Efficacy Belief and Burnout Level among Turkish Academicians

    ERIC Educational Resources Information Center

    Sevindi, Tarik

    2013-01-01

    The aim of this study is to examine the relation between burnout level and general self-efficacy beliefs of academicians working in School of Physical Education and Sport. 178 Academicians working at various universities in Turkey participated in this study. The General Self-Efficacy Scale developed by Schwarzer and Jerusalem (1995), adapted to…

  4. Genetic impoverishment and cross-incompatibility in remnant genotypes of Ziziphus celata (Rhamnaceae), a rare shrub endemic to the Lake Wales Ridge, Florida

    Treesearch

    C.W. Weekley; Thomas L. Kubisiak; T.M. Race

    2002-01-01

    The loss of genetic diversity in fragmented populations of self-incompalible plant species may result in sexual reproductive failure and local extinctions. Florida ziziphus (Ziziphus celata)is a self-incompetiblc clonal shrub known only from five genetically depauperate populations on the Lake Wales Ridge. Florida, USA. Recovery of this species...

  5. Academic Ethics in Turkish Universities: Perceptions of Academicians from Engineering, Medicine and Education Colleges

    ERIC Educational Resources Information Center

    Aydin, Inayet; Demirkasimoglu, Nihan; Alkin, Senar

    2012-01-01

    Problem Statement: Academicians such as scientists contribute to the research of knowledge, to the free disclosure of knowledge, to students' training, and to public service with their special knowledge and skills. Academicians' ethical responsibilities and values a very important place in the development of universities' functions, which, in…

  6. 27 CFR 9.127 - Cayuga Lake.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... Lake. (a) Name. The name of the viticultural area described in this section is “Cayuga Lake.” (b... of Lake Ridge. (6) Then follow State Route 34B in a generally southeast direction until it intersects...

  7. 27 CFR 9.127 - Cayuga Lake.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... Lake. (a) Name. The name of the viticultural area described in this section is “Cayuga Lake.” (b... of Lake Ridge. (6) Then follow State Route 34B in a generally southeast direction until it intersects...

  8. Health beliefs and breast self-examination in a sample of Turkish women academicians in a university.

    PubMed

    Ceber, Esin; Yücel, Ummahan; Mermer, Gülengül; Ozentürk, Gülsün

    2009-01-01

    The purpose of this study was to evaluate health beliefs and BSE behavior of female academicians in a Turkish university. This descriptive study was conducted at various faculties located in Ege University, Izmir, Turkey, in 2005. The sample consisted of 224 female academicians. Data were collected using a self-administered questionnaire and the Turkish version of Champion's Health Belief Model Scales (HBM). Descriptive statistics, t-test and Mann Whitney u analysis were conducted. The percentage of participants who regularly performed BSE was 27.7 %. Benefits and health motivation related to BSE ranked either first or second, along with confidence. Perceived barriers to BSE had the lowest item mean subscale score in academicians. Single academicians perceived susceptibility and seriousness higher than their married counterparts. Family history of breast cancer of participants affected their health beliefs subscale. BSE performance among participants was more likely in women academicians who exhibited higher confidence and those who perceived fewer barriers related to BSE performance, complying with the conceptual structure of the HBM. Therefore, it is recommended that in order to increase the rates of regular breast cancer screening, mass health protective programs based on the HBM should be executed for women.

  9. Geomorphic and sedimentologic evidence for the separation of Lake Superior from Lake Michigan and Huron

    USGS Publications Warehouse

    Johnston, J.W.; Thompson, T.A.; Wilcox, D.A.; Baedke, S.J.

    2007-01-01

    A common break was recognized in four Lake Superior strandplain sequences using geomorphic and sedimentologic characteristics. Strandplains were divided into lakeward and landward sets of beach ridges using aerial photographs and topographic surveys to identify similar surficial features and core data to identify similar subsurface features. Cross-strandplain, elevation-trend changes from a lowering towards the lake in the landward set of beach ridges to a rise or reduction of slope towards the lake in the lakeward set of beach ridges indicates that the break is associated with an outlet change for Lake Superior. Correlation of this break between study sites and age model results for the strandplain sequences suggest that the outlet change occurred sometime after about 2,400 calendar years ago (after the Algoma phase). Age model results from one site (Grand Traverse Bay) suggest an alternate age closer to about 1,200 calendar years ago but age models need to be investigated further. The landward part of the strandplain was deposited when water levels were common in all three upper Great Lakes basins (Superior, Huron, and Michigan) and drained through the Port Huron/Sarnia outlet. The lakeward part was deposited after the Sault outlet started to help regulate water levels in the Lake Superior basin. The landward beach ridges are commonly better defined and continuous across the embayments, more numerous, larger in relief, wider, have greater vegetation density, and intervening swales contain more standing water and peat than the lakeward set. Changes in drainage patterns, foreshore sediment thickness and grain size help in identifying the break between sets in the strandplain sequences. Investigation of these breaks may help identify possible gaps in the record or missing ridges in strandplain sequences that may not be apparent when viewing age distributions and may justify the need for multiple age and glacial isostatic adjustment models. ?? 2006 Springer Science

  10. The Relationship between Organizational Silence and Burnout among Academicians: A Research on Universities in Turkey

    ERIC Educational Resources Information Center

    Akin, Ugur; Ulusoy, Tarik

    2016-01-01

    The aim of this research is to analyze the relationship between organizational silence and burnout levels of academicians. The study group consisted of 190 academicians, who work in 17 state universities that are located in 15 different provinces of Turkey. Data were collected through Causes of Faculty Members' Silence Scale and Maslach Burnout…

  11. Top 12 Be-Attitudes of Netiquette for Academicians

    ERIC Educational Resources Information Center

    Berk, Ronald A.

    2011-01-01

    The term "netiquette" is the abbreviation for "network etiquette." It is derived from two French words: "net," meaning "bucket," and "iquette," meaning "of doilies." It is not new, dating back to 1983, but it certainly deserves the attention of both veteran and newbie Internet users, especially academicians. Rules for corresponding on the Internet…

  12. The Early Tech Development Course: Experiential Commercialization Education for the Medical Academician

    PubMed Central

    Chang, Connie; Fay, Jonathan; Ward, Kevin

    2017-01-01

    Problem Research produced by medical academicians holds promise for developing into biomedical innovations in therapeutics, devices, diagnostics, and health care information technology; however, the road to biomedical innovation is fraught with risk, including the challenge of moving from basic research insight onto a viable commercialization path. Compounding this challenge is the growing demand on medical academicians to be more productive in their clinical, teaching, and research duties within a resource-constrained environment. Approach In 2014, the University of Michigan (UM) Medical School and College of Engineering codesigned and implemented an accelerated, biomedical-focused version of the National Science Foundation (NSF) Innovation Corps (I-Corps) program. The UM Early Tech Development (ETD) Course, designed for medical academicians exploring the commercial potential of early-stage ideas, covers the NSF I-Corps concept; supports the formation of teams of faculty, graduate, and medical students; and accommodates medical academicians’ schedules. Outcomes From 2014 to 2015, the ETD Course graduated 39 project teams from UM and other institutions. One-third of the teams have continued to pursue their projects, receiving additional funding, engaging industry partners, or enrolling in the NSF I-Corps program. Next Steps The ETD Course, a potential pipeline to the NSF I-Corps program, captures a target audience of medical academicians and others in academic medicine. To better understand the long-term effects of the course and its relationship to the NSF I-Corps program, the authors will conduct a study on the careers of all ETD Course graduates, including those who have enrolled in NSF I-Corps versus those who have not. PMID:28351064

  13. Vivianite formation and distribution in Lake Baikal sediments

    NASA Astrophysics Data System (ADS)

    Fagel, N.; Alleman, L. Y.; Granina, L.; Hatert, F.; Thamo-Bozso, E.; Cloots, R.; André, L.

    2005-04-01

    In an effort to better understand vivianite formation processes, four Lake Baikal sediment cores spanning two to four interglacial stages in the northern, central and southern basins and under various biogeochemical environments are scrutinized. The vivianite-rich layers were detected by anomalous P-enrichments in bulk geochemistry and visually by observations on X-radiographs. The millimetric concretions of vivianite were isolated by sieving and analysed by X-ray diffraction, scanning electron microscope (SEM), microprobe, infrared spectroscopy, inductively coupled plasma atomic emission spectrometry and mass spectrometry (ICP-AES, ICP-MS). All the vivianites display similar morphological, mineralogical and geochemical signature, suggesting a common diagenetic origin. Their geochemical signature is sensitive to secondary alteration where vivianite concretions are gradually transformed from the rim to the center into an amorphous santabarbaraite phase with a decreasing Mn content. We analysed the spatial and temporal distribution of the concretions in order to determine the primary parameters controlling the vivianite formation, e.g., lithology, sedimentation rates, and porewater chemistry. We conclude that vivianite formation in Lake Baikal is mainly controlled by porewater chemistry and sedimentation rates, and it is not a proxy for lacustrine paleoproductivity. Vivianite accumulation is not restricted to areas of slow sedimentation rates (e.g., Academician and Continent ridges). At the site of relatively fast sedimentation rate, i.e., the Posolsky Bank near the Selenga Delta, vivianite production may be more or less related to the Selenga River inputs. It could be also indirectly related to the past intensive methane escapes from the sediments. While reflecting an early diagenetic signal, the source of P and Fe porewater for vivianites genesis is still unclear.

  14. Late Holocene lake-level variation in southeastern Lake Superior: Tahquamenon Bay, Michigan

    USGS Publications Warehouse

    Johnston, John W.; Baedke, Steve J.; Booth, Robert K.; Thompson, Todd A.; Wilcox, Douglas A.

    2004-01-01

    Internal architecture and ages of 71 beach ridges in the Tahquamenon Bay embayment along the southeastern shore of Lake Superior on the Upper Peninsula of Michigan were studied to generate a late Holocene relative lake-level curve. Establishing a long-term framework is important to examine the context of historic events and help predict potential future changes critical for effective water resource management. Ridges in the embayment formed between about 4,200 and 2,100 calendar years before 1950 (cal. yrs. B.P.) and were created and preserved every 28 A? 4.8 years on average. Groups of three to six beach ridges coupled with inflections in the lake-level curve indicate a history of lake levels fluctuations and outlet changes. A rapid lake-level drop (approximately 4 m) from about 4,100 to 3,800 cal. yrs. B.P. was associated with a fall from the Nipissing II high-water-level phase. A change from a gradual fall to a slight rise was associated with an outlet change from Port Huron, Michigan/Sarnia, Ontario to Sault Ste. Marie, Michigan/Ontario. A complete outlet change occurred after the Algoma high-water-level phase (ca. 2,400 cal. yrs. B.P.). Preliminary rates of vertical ground movement calculated from the strandplain are much greater than rates calculated from historical and geologic data. High rates of vertical ground movement could have caused tectonism in the Whitefish Bay area, modifying the strandplain during the past 2,400 years. A tectonic event at or near the Sault outlet also may have been a factor in the outlet change from Port Huron/Sarnia to Sault Ste. Marie.

  15. 27 CFR 9.215 - Lake Chelan.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... purposes of part 4 of this chapter, “Lake Chelan” and “Chelan” are terms of viticultural significance. (b... Co., 1968, photorevised 1987; (2) Cooper Ridge Quadrangle—Washington, 1968, photorevised 1987; (3... meandering 2,000-foot elevation line generally southeast onto the Cooper Ridge map, crossing Purtterman Gulch...

  16. 27 CFR 9.215 - Lake Chelan.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... purposes of part 4 of this chapter, “Lake Chelan” and “Chelan” are terms of viticultural significance. (b... Co., 1968, photorevised 1987; (2) Cooper Ridge Quadrangle—Washington, 1968, photorevised 1987; (3... meandering 2,000-foot elevation line generally southeast onto the Cooper Ridge map, crossing Purtterman Gulch...

  17. Evidence of Lake Trout reproduction at Lake Michigan's mid-lake reef complex

    USGS Publications Warehouse

    Janssen, J.; Jude, D.J.; Edsall, T.A.; Paddock, R.W.; Wattrus, N.; Toneys, M.; McKee, P.

    2006-01-01

    The Mid-Lake Reef Complex (MLRC), a large area of deep (> 40 m) reefs, was a major site where indigenous lake trout (Salvelinus namaycush) in Lake Michigan aggregated during spawning. As part of an effort to restore Lake Michigan's lake trout, which were extirpated in the 1950s, yearling lake trout have been released over the MLRC since the mid-1980s and fall gill net censuses began to show large numbers of lake trout in spawning condition beginning about 1999. We report the first evidence of viable egg deposition and successful lake trout fry production at these deep reefs. Because the area's existing bathymetry and habitat were too poorly known for a priori selection of sampling sites, we used hydroacoustics to locate concentrations of large fish in the fall; fish were congregating around slopes and ridges. Subsequent observations via unmanned submersible confirmed the large fish to be lake trout. Our technological objectives were driven by biological objectives of locating where lake trout spawn, where lake trout fry were produced, and what fishes ate lake trout eggs and fry. The unmanned submersibles were equipped with a suction sampler and electroshocker to sample eggs deposited on the reef, draw out and occasionally catch emergent fry, and collect egg predators (slimy sculpin Cottus cognatus). We observed slimy sculpin to eat unusually high numbers of lake trout eggs. Our qualitative approaches are a first step toward quantitative assessments of the importance of lake trout spawning on the MLRC.

  18. An Attempt for the Exploration of Academicians' Experiences of the Standard Foreign Language Tests Held in Turkey through Metaphors

    ERIC Educational Resources Information Center

    Yesilyurt, Savas

    2016-01-01

    The purpose of this study is to explore academicians' perceptions and experiences about the public high-stakes Foreign Language Test(s) (YDS, formerly UDS, KPDS, and their counterparts in different times and contexts) used to measure foreign language proficiency in Turkey. For this purpose, data were collected from academicians with different…

  19. Polygonal Ridge Networks on Mars

    NASA Astrophysics Data System (ADS)

    Kerber, Laura; Dickson, James; Grosfils, Eric; Head, James W.

    2016-10-01

    Polygonal ridge networks, also known as boxwork or reticulate ridges, are found in numerous locations and geological contexts across Mars. While networks formed from mineralized fractures hint at hot, possibly life-sustaining circulating ground waters, networks formed by impact-driven clasting diking, magmatic dikes, gas escape, or lava flows do not have the same astrobiological implications. Distinguishing the morphologies and geological context of the ridge networks sheds light on their potential as astrobiological and mineral resource sites of interest. The most widespread type of ridge morphology is characteristic of the Nili Fossae and Nilosyrtis region and consists of thin, criss-crossing ridges with a variety of heights, widths, and intersection angles. They are found in ancient Noachian terrains at a variety of altitudes and geographic locations and may be a mixture of clastic dikes, brecciated dikes, and mineral veins. They occur in the same general areas as valley networks and ancient lake basins, but they are not more numerous where these features are concentrated, and can appear in places where they morphologies are absent. Similarly, some of the ridge networks are associated with hydrated mineral detections, but some occur in locations without detections. Smaller, light-toned ridges of variable widths have been found in Gale Crater and other rover sites and are interpreted to be smaller version of the Nili-like ridges, in this case formed by the mineralization of fractures. This type of ridge is likely to be found in many other places on Mars as more high-resolution data becomes available. Hellas Basin is host to a third type of ridge morphology consisting of large, thick, light-toned ridges forming regular polygons at several superimposed scales. While still enigmatic, these are most likely to be the result of sediment-filled fractures. The Eastern Medusae Fossae Formation contains large swaths of a fourth, previously undocumented, ridge network type

  20. Faulting along the southern margin of Reelfoot Lake, Tennessee

    USGS Publications Warehouse

    Van Arsdale, R.; Purser, J.; Stephenson, W.; Odum, J.

    1998-01-01

    The Reelfoot Lake basin, Tennessee, is structurally complex and of great interest seismologically because it is located at the junction of two seismicity trends of the New Madrid seismic zone. To better understand the structure at this location, a 7.5-km-long seismic reflection profile was acquired on roads along the southern margin of Reelfoot Lake. The seismic line reveals a westerly dipping basin bounded on the west by the Reelfoot reverse fault zone, the Ridgely right-lateral transpressive fault zone on the east, and the Cottonwood Grove right-lateral strike-slip fault in the middle of the basin. The displacement history of the Reelfoot fault zone appears to be the same as the Ridgely fault zone, thus suggesting that movement on these fault zones has been synchronous, perhaps since the Cretaceous. Since the Reelfoot and Ridgely fault systems are believed responsible for two of the mainshocks of 1811-1812, the fault history revealed in the Reelfoot Lake profile suggests that multiple mainshocks may be typical of the New Madrid seismic zone. The Ridgely fault zone consists of two northeast-striking faults that lie at the base of and within the Mississippi Valley bluff line. This fault zone has 15 m of post-Eocene, up-to-the-east displacement and appears to locally control the eastern limit of Mississippi River migration. The Cottonwood Grove fault zone passes through the center of the seismic line and has approximately 5 m up-to-the-east displacement. Correlation of the Cottonwood Grove fault with a possible fault scarp on the floor of Reelfoot Lake and the New Markham fault north of the lake suggests the Cottonwood Grove fault may change to a northerly strike at Reelfoot Lake, thereby linking the northeast-trending zones of seismicity in the New Madrid seismic zone.

  1. Aspiration to Enrol Children in Islamic Studies: A Case of Academicians

    ERIC Educational Resources Information Center

    Islam, Tazul; Zayed, Tareq M.

    2016-01-01

    Purpose: A preliminary observation reveals that children of Islamic studies (IS) academicians do not choose IS as their career discipline. In view of this, this paper aims to explore the dimensions of parental attitudes, behaviours, perceptions and aspirations in seeing a future in IS for their children. Design/methodology/approach: Fifteen…

  2. Tsunami-induced morphological change of a coastal lake: comparing hydraulic experiment with numerical modeling

    NASA Astrophysics Data System (ADS)

    Sugawara, D.; Imai, K.; Mitobe, Y.; Takahashi, T.

    2016-12-01

    Coastal lakes are one of the promising environments to identify deposits of past tsunamis, and such deposits have been an important key to know the recurrence of tsunami events. In contrast to tsunami deposits on the coastal plains, however, relationship between deposit geometry and tsunami hydrodynamic character in the coastal lakes has poorly been understood. Flume experiment and numerical modeling will be important measures to clarify such relationship. In this study, data from a series of flume experiment were compared with simulations by an existing tsunami sediment transport model to examine applicability of the numerical model for tsunami-induced morphological change in a coastal lake. A coastal lake with a non-erodible beach ridge was modeled as the target geomorphology. The ridge separates the lake from the offshore part of the flume, and the lake bottom was filled by sand. Tsunami bore was generated by a dam-break flow, which is capable of generating a maximum near-bed flow speed of 2.5 m/s. Test runs with varying magnitude of the bore demonstrated that the duration of tsunami overflow controls the scouring depth of the lake bottom behind the ridge. The maximum scouring depth reached up to 7 cm, and sand deposition occurred mainly in the seaward-half of the lake. A conventional depth-averaged tsunami hydrodynamic model coupled with the sediment transport model was used to compare the simulation and experimental results. In the Simulation, scouring depth behind the ridge reached up to 6 cm. In addition, the width of the scouring was consistent between the simulation and experiment. However, sand deposition occurred mainly in a zone much far from the ridge, showing a considerable deviation from the experimental results. This may be associated with the lack of model capability to resolve some important physics, such as vortex generation behind the ridge and shoreward migration of hydraulic jump. In this presentation, the results from the flume experiment and

  3. An Empirical Inquiry on Knowledge Sharing among Academicians in Higher Learning Institutions

    ERIC Educational Resources Information Center

    Ramayah, T.; Yeap, Jasmine A. L.; Ignatius, Joshua

    2013-01-01

    Universities are expected to be places where knowledge is shared freely among academicians. However, the reality shows that knowledge sharing is barely present within universities these days. As Malaysia shifts towards building a knowledge-based society, academic institutions, particularly the public universities, now face ever-growing faculty…

  4. Stable isotope ratios in swale sequences of Lake Superior as indicators of climate and lake level fluctuations during the Late Holocene

    USGS Publications Warehouse

    Sharma, Shruti; Mora, G.; Johnston, J.W.; Thompson, T.A.

    2005-01-01

    Beach ridges along the coastline of Lake Superior provide a long-term and detailed record of lake level fluctuations for the past 4000 cal BP. Although climate change has been invoked to explain these fluctuations, its role is still in debate. Here, we reconstruct water balance by employing peat samples collected from swale deposits present between beach ridge sequences at two locations along the coastline of Lake Superior. Carbon isotope ratios for Sphagnum remains from these peat deposits are used as a proxy for water balance because the presence or absence of water films on Sphagnum controls the overall isotope discrimination effects. Consequently, increased average water content in Sphagnum produces elevated ??13C values. Two maxima of Sphagnum ??13C values interpreted to reflect wetter conditions prevailed from 3400 to 2400 cal BP and from about 1900 to 1400 cal BP. There are two relatively short drier periods as inferred from low Sphagnum ??13C values: one is centered at about 2300 cal BP, and one begins at 1400 cal BP. A good covariance was found between Sphagnum ??13C values and reconstructed lake-levels for Lake Michigan in which elevated carbon isotope values correlate well with higher lake levels. Based on this covariance, we conclude that climate exerts a strong influence on lake levels in Lake Superior for the past 4000 cal BP. ?? 2005 Elsevier Ltd. All rights reserved.

  5. Research Publication Output by Academicians in Public and Private Universities in Malaysia

    ERIC Educational Resources Information Center

    Suryani, Ina; Yaacob, Aizan; Hashima, Noor; Rashid, Salleh Abd; Desa, Hazry

    2013-01-01

    The number of publication has been one of the measurement values in the performance evaluation for higher education academicians. Over the years, the obligation to publish has amplified to not just on getting published but also on getting published in high quality journal whereby the quality ranking is determined by publication categories. This…

  6. Stochastic modelling for lake thermokarst and peatland patterns in permafrost and near permafrost zones

    NASA Astrophysics Data System (ADS)

    Orlov, Timofey; Sadkov, Sergey; Panchenko, Evgeniy; Zverev, Andrey

    2017-04-01

    Peatlands occupy a significant share of the cryolithozone area. They are currently experiencing an intense affection by oil and gas field development, as well as by the construction of infrastructure. That poses the importance of the peatland studies, including those dealing with the forecast of peatland evolution. Earlier we conducted a similar probabilistic modelling for the areas of thermokarst development. Principle points of that were: 1. Appearance of a thermokarst depression within an area given is the random event which probability is directly proportional to the size of the area ( Δs). For small sites the probability of one thermokarst depression to appear is much greater than that for several ones, i.e. p1 = γ Δs + o (Δs) pk = o (Δs) \\quad k=2,3 ... 2. Growth of a new thermokarst depression is a random variable independent on other depressions' growth. It happens due to thermoabrasion and, hence, is directly proportional to the amount of heat in the lake and is inversely proportional to the lateral surface area of the lake depression. By using this model, we are able to get analytically two main laws of the morphological pattern for lake thermokarst plains. First, the distribution of a number of thermokarst depressions (centers) at a random plot obey the Poisson law: P(k,s) = (γ s)^k/k! e-γ s. where γ is an average number of depressions per area unit, s is a square of a trial sites. Second, lognormal distribution of diameters of thermokarst lakes is true at any time, i.e. density distribution is given by the equation: fd (x,t)=1/√{2πσ x √{t}} e-ridge-lake patterns. Ridge-hollow structures RHS possess a specific implication in a peatland functioning system. They are associated with the surface and underground water flows, as well as with the

  7. 9. VIEW FROM MANY PARKS CURVE (ON TRAIL RIDGE ROAD) ...

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

    9. VIEW FROM MANY PARKS CURVE (ON TRAIL RIDGE ROAD) OF HORSESHOE PARK, SHOWING FALL RIVER ROAD FAINTLY AT LEFT AT BASE OF SHEEP MOUNTAIN AND CROSSING ALLUVIAL FAN FROM LAWN LAKE FLOOD. - Fall River Road, Between Estes Park & Fall River Pass, Estes Park, Larimer County, CO

  8. 75 FR 49517 - Notice of Intent To Prepare an Environmental Impact Statement for the Walker Ridge Wind Project...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-08-13

    ... system. The proposed action would include up to 42 wind turbine generators, an underground electrical...] Notice of Intent To Prepare an Environmental Impact Statement for the Walker Ridge Wind Project, Lake and...: You may submit comments related to the Walker Ridge Wind Project by any of the following methods: Web...

  9. Remedial Investigation Report on Chestnut Ridge Operable Unit 2 (Filled Coal Ash Pond/Upper McCoy Branch) at the Oak Ridge Y-12 Plant, Oak Ridge, Tennessee. Volume 1. Main Text

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Not Available

    1994-08-01

    This document is a report on the remedial investigation (RI) of Chestnut Ridge Operable Unit (OU) 2 at the Oak Ridge Y-12 Plant. Chestnut Ridge OU 2 consists of Upper McCoy Branch (UMB), the Filled Coal Ash Pond (FCAP), and the area surrounding the Sluice Channel formerly associated with coal ash disposal in the FCAP. Chestnut Ridge OU 2 is located within the U.S. Department of Energy`s (DOE`s) Oak Ridge Reservation in Anderson County, Tennessee, approximately 24 miles west of Knoxville. The pond is an 8.5-acre area on the southern slope of Chestnut Ridge, 0.5 mile south of the mainmore » Y-12 Plant and geographically separated from the Y-12 Plant by Chestnut Ridge. The elevation of the FCAP is {approximately} 950 ft above mean sea level (msl), and it is relatively flat and largely vegetated. Two small ponds are usually present at the northeast and northwest comers of the FCAP. The Sluice Channel Area extends {approximately}1000 ft from the northern margin of the FCAP to the crest of Chestnut Ridge, which has an elevation of {approximately}1100 ft above msl. The Sluice Channel Area is largely vegetated also. McCoy Branch runs from the top of Chestnut Ridge across the FCAP into Rogers Quarry and out of the quarry where it runs a short distance into Milton Hill Lake at McCoy Embayment, termed UMB. The portion south of Rogers Quarry, within Chestnut Ridge OU 4, is termed Lower McCoy Branch. The DOE Oak Ridge Y-12 Plant disposed of coal ash from its steam plant operations as a slurry that was discharged into an ash retention impoundment; this impoundment is the FCAP. The FCAP was built in 1955 to serve as a settling basin after coal ash slurried over Chestnut Ridge from the Y-12 Plant. The FCAP was constructed by building an earthen dam across the northern tributary of McCoy Branch. The dam was designed to hold 20 years of Y-12 steam plant ash. By July 1967, ash had filled up the impoundment storage behind the dam to within 4 ft of the top.« less

  10. The Impact of Interpersonal Discrimination and Stress on Health and Performance for Early Career STEM Academicians

    PubMed Central

    O’Brien, Katharine R.; McAbee, Samuel T.; Hebl, Michelle R.; Rodgers, John R.

    2016-01-01

    The present study examines the consequences of perceived interpersonal discrimination on stress, health, and performance in a sample of 210 science, technology, engineering, and mathematics (STEM) academicians. Using a path model, we test the relation that perceived interpersonal discrimination has on stress and the relation of stress to physical health maladies and on current and future performance. In so doing, we assess the link between discrimination and decrements in performance over time. Additionally, we test supervisor social support as a moderator of the discrimination–stress relation. Findings support relations between perceived interpersonal discrimination and stress, which in turn relates to declines in physical health and performance outcomes. Moreover, supervisory support is shown to mitigate the influence of interpersonal discrimination on stress in STEM academicians. PMID:27199848

  11. Cultural Resources Investigations, Norfork Lake, Arkansas

    DTIC Science & Technology

    1986-07-01

    Salem PlateauSBig Creek Ecozone Intensive Survey Terraces Bracher Ridge Foraging Norfork Lake 20. ABSTRACT (Conrihm o revere aide Of necessay and...with an intensification of regional exploitation of ecozones . During this period, point style proliferation and variation is interpreted as a

  12. Turkish EFL Academicians' Problems Concerning Translation Activities and Practices, Attitudes towards the Use of Online and Printed Translation Tools, and Suggestions for Quality Translation Practice

    ERIC Educational Resources Information Center

    Zengin, Bugra; Kacar, Isil Gunseli

    2011-01-01

    This mixed method research study aimed to highlight the problems of EFL academicians concerning their current translation practices, their attitudes towards the use of various translation tools, and offer suggestions for more quality translation practices. Seventy-three EFL academicians from three Turkish universities participated in the study.…

  13. The Effects of Culture on Psychological Mobility: Comparative Analyses of Turkish and Canadian Academicians

    ERIC Educational Resources Information Center

    Erdogmus, Nihat; Aytekin, Ihsan

    2012-01-01

    The present study comparatively examines the effects of culture on psychological mobility of academicians in Turkey and Canada. Questionnaires were completed by 382 respondents, of them 277 Turkish and 105 Canadian. Data were collected using INDCOL for measuring the four cultural dimensions. Psychological mobility that consisted of boundaryless…

  14. Physical metallurgy: Scientific school of the Academician V.M. Schastlivtsev

    NASA Astrophysics Data System (ADS)

    Tabatchikova, T. I.

    2016-04-01

    This paper is to honor Academician Vadim Mikhailovich Schastlivtsev, a prominent scientist in the field of metal physics and materials science. The article comprises an analysis of the topical issues of the physical metallurgy of the early 21st century and of the contribution of V.M. Schastlivtsev and of his school to the science of phase and structural transformations in steels. In 2015, Vadim Mikhailovich celebrates his 80th birthday, and this paper is timed to this honorable date. The list of his main publications is given in it.

  15. The Value Preferences of the Academicians in Turkey towards Their Children, Students, and Colloquies

    ERIC Educational Resources Information Center

    Ozdemir, M. Cagatay; Unsal, Haluk; Yuksel, Galip; Cemaloglu, Necati

    2010-01-01

    The purpose of this study is to determine the preferences of Turkish academicians about the values of the most positive and negative characteristics that they want to see in their children, students, and colleagues. In this study, Bacanli's (2002) "the most positive" and "the most negative" adjectives data gathering tool is…

  16. Newly Collected Multibeam Swath Bathymetry Data Herald a New Phase in Gas-hydrate Research on Lake Baikal

    NASA Astrophysics Data System (ADS)

    Naudts, L.; Khlystov, O.; Khabuev, A.; Seminskiy, I.; Casier, R.; Cuylaerts, M.; 'chenko, P., General; Synaeve, J.; Vlamynck, N.; de Batist, M. A.; Grachev, M. A.

    2009-12-01

    Lake Baikal is a large rift lake in Southern Siberia (Russian Federation). It occupies the three central depressions of the Baikal Rift Zone (BRZ): i.e. the Southern, Central and Northern Baikal Basins. Rifting started ca. 30 Ma ago and is still active with a present-day average extension rate of about 4 mm/yr. With a depth of 1637 m, Lake Baikal is the deepest lake in the World. It also holds 20 % of the world’s liquid surface fresh water, which makes it the largest lake in the World in terms of volume. Lake Baikal is also the only freshwater lake in the World with demonstrated occurrences of gas hydrates in its sedimentary infill. Methane hydrates are stable at water depths below 375 m. The presence of hydrates in the sedimentary infill is evidenced by a widespread BSR. Hydrates have also been encountered locally, in the near-bottom sediments of mud-volcano-like structures. In the summer of 2009, the lake floor has been mapped with multibeam swath bathymetry for the first time during a two-month-long survey with RV Titov. Swath bathymetry data were acquired with RCMG’s mobile 50 kHz SeaBeam 1050 multibeam system. In total 12600 km of echosounder tracks were sailed covering 15000 km2, including the Academician Ridge Accommodation Zone, the Central Baikal Basin, the Selenga Delta Accommodation Zone en the South Baikal Basin. In general, the lake floor was mapped starting from water depths of about -200 m to -1637 m, with an average survey depth of -1000 m. The new bathymetric data image the lake-floor morphology in unprecedented detail, revealing many small- and large-scall morphosedimentary, morphostructural and fluid-flow-related features, many of which were hitherto unknown. Known mud-volcano provinces in the Southern and Central Baikal Basins (i.e. the Posolsky Bank mud-volcano province, the Kukuy Canyon mud volcano province and the Olkhon Gate mud-volcano province) were mapped in detail, and several new, often isolated, mud-volcano-like structures were

  17. Ridge suction drives plume-ridge interactions

    NASA Astrophysics Data System (ADS)

    Niu, Y.; Hékinian, R.

    2003-04-01

    Deep-sourced mantle plumes, if existing, are genetically independent of plate tectonics. When the ascending plumes approach lithospheric plates, interactions between the two occur. Such interactions are most prominent near ocean ridges where the lithosphere is thin and the effect of plumes is best revealed. While ocean ridges are mostly passive features in terms of plate tectonics, they play an active role in the context of plume-ridge interactions. This active role is a ridge suction force that drives asthenospheric mantle flow towards ridges because of material needs to form the ocean crust at ridges and lithospheric mantle in the vicinity of ridges. This ridge suction force increases with increasing plate separation rate because of increased material demand per unit time. As the seismic low-velocity zone atop the asthenosphere has the lowest viscosity that increases rapidly with depth, the ridge-ward asthenospheric flow is largely horizontal beneath the lithosphere. Recognizing that plume materials have two components with easily-melted dikes/veins enriched in volatiles and incompatible elements dispersed in the more refractory and depleted peridotitic matrix, geochemistry of some seafloor volcanics well illustrates that plume-ridge interactions are consequences of ridge-suction-driven flow of plume materials, which melt by decompression because of lithospheric thinning towards ridges. There are excellent examples: 1. The decreasing La/Sm and increasing MgO and CaO/Al_2O_3 in Easter Seamount lavas from Salas-y-Gomez Islands to the Easter Microplate East rift zone result from progressive decompression melting of ridge-ward flowing plume materials. 2. The similar geochemical observations in lavas along the Foundation hotline towards the Pacific-Antarctic Ridge result from the same process. 3. The increasing ridge suction force with increasing spreading rate explains why the Iceland plume has asymmetric effects on its neighboring ridges: both topographic and

  18. Comparison of evaporation at two central Florida lakes, April 2005–November 2007

    USGS Publications Warehouse

    Swancar, Amy

    2015-09-25

    Both lakes are seepage lakes (no surface-water inflow or outflows) that are dependent on groundwater inflow from their basins to offset an atmospheric deficit, because long-term rainfall in this area is less than evaporation. The Lake Starr basin, where sandy, well-drained ridges surround the lake, has a greater capacity to store infiltrating rain than the Lake Calm basin, which is flat and has poorly drained soils. The storage capacities of the basins affect groundwater exchange with the lakes. Rainfall and net groundwater exchange, which is related to basin characteristics, varied more between these two lakes than did evaporation during this study.

  19. 32. Otter Lake Dam. View from downstream show how the ...

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

    32. Otter Lake Dam. View from downstream show how the dam blends into its environment. Looking east-northeast. - Blue Ridge Parkway, Between Shenandoah National Park & Great Smoky Mountains, Asheville, Buncombe County, NC

  20. Academician V.F. Utkin, General Designer of Space Launch Systems

    NASA Astrophysics Data System (ADS)

    Konyukhov, S.; Novykov, O.

    2002-01-01

    Academician Vladimir Fedorovich Utkin was an outstanding scientist and designer of rocket and space machinery, Doctor of Technical Science, Professor, Twice Hero of Socialist Labor, Lenin Prize and USSR State Prize winner, bearer of six Orders of Lenin and many other government awards. For 19 years, 1971 - 1990, V. F. Utkin held a position of General Designer in Yuzhnoye SDO having inherited this post from Academician Mikhail Kuzmich Yangel - Yuhnoye's founder. From 1990 till 2000 V. F. Utkin headed Central Scientific Research Institute of Machinery of Russia (TsNIIMash) as its General Designer. Under leadership of V. F. Utkin Yuzhnoye SDO designed several generations of unique strategic missile systems that laid the foundation for Rocket Strategic Forces of the Soviet Union and Russia, subsequently, developed one of the largest high-performance liquid- propellant ICBM SS-18 (Satan), solid-propellant ICBM SS-24 designed for both silo and rail- road deployment, environment friendly Zenit launch vehicle, delivered more than three hundred military, scientific and environmental satellites with tasks. A series of complicated scientific and technical problems has been resolved, a number of unique designing and technological solutions has been implemented in course of development, e.g. separating and orbital warheads, pop-up launch of heavy missiles from a container, continuous and persistent combat duty of liquid-propellant missiles, missile tolerance to nuclear explosion damage, liberation of vessels from ice captivity in the Arctic Ocean using Cosmos-1500 satellite - ancestor of the Ocean satellite constellation designed for accomplishment of seafaring tasks. The existing Russian Program for Rocket and Space Machinery development was designed under leadership of V.F. Utkin.

  1. Evidence for early hunters beneath the Great Lakes.

    PubMed

    O'Shea, John M; Meadows, Guy A

    2009-06-23

    Scholars have hypothesized that the poorly understood and rarely encountered archaeological sites from the terminal Paleoindian and Archaic periods associated with the Lake Stanley low water stage (10,000-7,500 BP) are lost beneath the modern Great Lakes. Acoustic and video survey on the Alpena-Amberley ridge, a feature that would have been a dry land corridor crossing the Lake Huron basin during this time period, reveals the presence of a series of stone features that match, in form and location, structures used for caribou hunting in both prehistoric and ethnographic times. These results present evidence for early hunters on the Alpena-Amberley corridor, and raise the possibility that intact settlements and ancient landscapes are preserved beneath Lake Huron.

  2. Evidence for early hunters beneath the Great Lakes

    PubMed Central

    O'Shea, John M.; Meadows, Guy A.

    2009-01-01

    Scholars have hypothesized that the poorly understood and rarely encountered archaeological sites from the terminal Paleoindian and Archaic periods associated with the Lake Stanley low water stage (10,000–7,500 BP) are lost beneath the modern Great Lakes. Acoustic and video survey on the Alpena-Amberley ridge, a feature that would have been a dry land corridor crossing the Lake Huron basin during this time period, reveals the presence of a series of stone features that match, in form and location, structures used for caribou hunting in both prehistoric and ethnographic times. These results present evidence for early hunters on the Alpena-Amberley corridor, and raise the possibility that intact settlements and ancient landscapes are preserved beneath Lake Huron. PMID:19506245

  3. The Investigation of Academicians' Learning Styles in School of Physical Education and Sports in Turkey

    ERIC Educational Resources Information Center

    Caglayan, Hakan Salim

    2011-01-01

    This study was carried out with the purpose of determining the academicians' learning styles in school of physical education and sports and whether there was a relationship between their learning styles and gender, age, appellation and the department they worked or not. In the study survey method that was used. The sample of the study consisted of…

  4. Morphological signatures of microbial activity across sediment and light microenvironments of Lake Vanda, Antarctica

    NASA Astrophysics Data System (ADS)

    Mackey, Tyler J.; Sumner, Dawn Y.; Hawes, Ian; Jungblut, Anne D.

    2017-11-01

    Cyanobacteria-dominated microbial mats in Lake Vanda grow with pinnacles and ridges separated by prostrate mat. Rocks protrude over microbial mats on the lake bottom to create localized, dm-scale gradients in sedimentation and irradiance. The effects of sedimentation on pinnacle and ridge growth were isolated from photosynthetic activity by contrasting growth across microenvironmental gradients. Sedimentation rate was measured as the mass of sand and mud sized sediment in mat that accumulated over 11 years, and the incident light was modeled near and under rocks by reconstructing topography using Structure from Motion techniques. Morphologically diverse pinnacles and ridges were documented in both exposed and sheltered mat microenvironments, in addition to growing downward from the underside of overhanging rocks. Mat that grew with > 40% irradiance under overhangs did not have consistent differences in pinnacle density or ridge abundance as a function of sedimentation rates or irradiance when compared to exposed mat. However, their morphology did change significantly with changes in the direction of incident irradiance. Where irradiance was < 40% ambient or light intersected the mat at very low angles, few pinnacles were present and ridges were preferentially aligned parallel to incident light direction. These observations indicate that pinnacle nucleation and spacing were not strongly influenced by sedimentation but pinnacle and ridge morphology varied in response to directional irradiance.

  5. Repeat ridge jumps associated with plume-ridge interaction, melt transport, and ridge migration

    NASA Astrophysics Data System (ADS)

    Mittelstaedt, Eric; Ito, Garrett; van Hunen, Jeroen

    2011-01-01

    Repeated shifts, or jumps, of mid-ocean ridge segments toward nearby hot spots can produce large, long-term changes to the geometry and location of the tectonic plate boundaries. Ridge jumps associated with hot spot-ridge interaction are likely caused by several processes including shear on the base of the plate due to expanding plume material as well as reheating of lithosphere as magma passes through it to feed off-axis volcanism. To study how these processes influence ridge jumps, we use numerical models to simulate 2-D (in cross section) viscous flow of the mantle, viscoplastic deformation of the lithosphere, and melt migration upward from the asthenospheric melting zone, laterally along the base of the lithosphere, and vertically through the lithosphere. The locations and rates that magma penetrates and heats the lithosphere are controlled by the time-varying accumulation of melt beneath the plate and the depth-averaged lithospheric porosity. We examine the effect of four key parameters: magmatic heating rate of the lithosphere, plate spreading rate, age of the seafloor overlying the plume, and the plume-ridge migration rate. Results indicate that the minimum value of the magmatic heating rate needed to initiate a ridge jump increases with plate age and spreading rate. The time required to complete a ridge jump decreases with larger values of magmatic heating rate, younger plate age, and faster spreading rate. For cases with migrating ridges, models predict a range of behaviors including repeating ridge jumps, much like those exhibited on Earth. Repeating ridge jumps occur at moderate magmatic heating rates and are the result of changes in the hot spot magma flux in response to magma migration along the base of an evolving lithosphere. The tendency of slow spreading to promote ridge jumps could help explain the observed clustering of hot spots near the Mid-Atlantic Ridge. Model results also suggest that magmatic heating may significantly thin the lithosphere

  6. Relationship between Organizational Justice Perceptions and Organizational Commitment Levels of School of Physical Education and Sports Academicians

    ERIC Educational Resources Information Center

    Ari, Abdil; Çaglayan, Hakan Salim

    2017-01-01

    This study was conducted to determine organizational justice perceptions and organizational commitment levels of the school of physical education and sports academicians and to establish whether there is a relation between their organizational justice perceptions and organizational commitment levels or not. In the study, a method for the…

  7. Antarctic lakes (above and beneath the ice sheet): Analogues for Mars

    NASA Technical Reports Server (NTRS)

    Rice, J. W., Jr.

    1992-01-01

    The perennial ice covered lakes of the Antarctic are considered to be excellent analogues to lakes that once existed on Mars. Field studies of ice covered lakes, paleolakes, and polar beaches were conducted in the Bunger Hills Oasis, Eastern Antarctica. These studies are extended to the Dry Valleys, Western Antarctica, and the Arctic. Important distinctions were made between ice covered and non-ice covered bodies of water in terms of the geomorphic signatures produced. The most notable landforms produced by ice covered lakes are ice shoved ridges. These features form discrete segmented ramparts of boulders and sediments pushed up along the shores of lakes and/or seas. Sub-ice lakes have been discovered under the Antarctic ice sheet using radio echo sounding. These lakes occur in regions of low surface slope, low surface accumulations, and low ice velocity, and occupy bedrock hollows. The presence of sub-ice lakes below the Martian polar caps is possible. The discovery of the Antarctic sub-ice lakes raises possibilities concerning Martian lakes and exobiology.

  8. Plume-ridge interaction: Shaping the geometry of mid-ocean ridges

    NASA Astrophysics Data System (ADS)

    Mittelstaedt, Eric L.

    Manifestations of plume-ridge interaction are found across the ocean basins. Currently there are interactions between at least 21 hot spots and nearby ridges along 15--20% of the global mid-ocean ridge network. These interactions produce a number of anomalies including the presence of elevated topography, negative gravity anomalies, and anomalous crustal production. One form of anomalous crustal production is the formation of volcanic lineaments between hotspots and nearby mid-ocean ridges. In addition, observations indicate that mantle plumes tend to "capture" nearby mid-ocean ridges through asymmetric spreading, increased ridge propagation, and discrete shifts of the ridge axis, or ridge jumps. The initiation of ridge jumps and the formation of off-axis volcanic lineaments likely involve similar processes and may be closely related. In the following work, I use theoretical and numerical models to quantify the processes that control the formation of volcanic lineaments (Chapter 2), the initiation of mid-ocean ridge jumps associated with lithospheric heating due to magma passing through the plate (Chapter 3), and the initiation of jumps due to an upwelling mantle plume and magmatic heating governed by melt migration (Chapter 4). Results indicate that lineaments and ridge jumps associated with plume-ridge interaction are most likely to occur on young lithosphere. The shape of lineaments on the seafloor is predicted to be controlled by the pattern of lithospheric stresses associated with a laterally spreading, near-ridge mantle plume. Ridge jumps are likely to occur due to magmatic heating alone only in lithosphere ˜1Myr old, because the heating rate required to jump increases with spreading rate and plate age. The added effect of an upwelling plume introduces competing effects that both promote and inhibit ridge jumps. For models where magmatic heating is controlled by melt migration, repeat ridge jumps are predicted to occur as the plume and ridge separate, but

  9. Were lakes on early Mars perennially were ice-covered?

    NASA Astrophysics Data System (ADS)

    Sumner, D. Y.; Rivera-Hernandez, F.; Mackey, T. J.

    2016-12-01

    Paleo-lake deposits indicate that Mars once sustained liquid water, supporting the idea of an early "wet and warm" Mars. However, liquid water can be sustained under ice in cold conditions as demonstrated by perennially ice-covered lakes (PICLs) in Antarctica. If martian lakes were ice-covered, the global climate on early Mars could have been much colder and dryer than if the atmosphere was in equilibrium with long-lived open water lakes. Modern PICLs on Earth have diagnostic sedimentary features. Unlike open water lakes that are dominated by mud, and drop stones or tills if icebergs are present, previous studies determined that deposits in PICLs can include coarser grains that are transported onto the ice cover, where they absorb solar radiation, melt through the ice and are deposited with lacustrine muds. In Lake Hoare, Antarctica, these coarse grains form conical sand mounds and ridges. Our observations of ice-covered lakes Joyce, Fryxell, Vanda and Hoare, Antarctica suggest that the distributions of grains depend significantly on ice characteristics. Deposits in these lakes contain moderately well to moderately sorted medium to very coarse sand grains, which preferentially melt through the ice whereas granules and larger grains remain on the ice surface. Similarly, high albedo grains are concentrated on the ice surface, whereas low albedo grains melt deeper into the ice, demonstrating a segregation of grains due to ice-sediment interactions. In addition, ice cover thickness may determine the spatial distribution of sand deposited in PICLs. Localized sand mounds and ridges composed of moderately sorted sand are common in PICLs with rough ice covers greater than 3 m thick. In contrast, lakes with smooth and thinner ice have disseminated sand grains and laterally extensive sand layers but may not have sand mounds. At Gale Crater, Mars, the Murray formation consists of sandy lacustrine mudstones, but the depositional process for the sand is unknown. The presence of

  10. Lake Afrera, a structural depression in the Northern Afar Rift (Red Sea).

    PubMed

    Bonatti, Enrico; Gasperini, Elia; Vigliotti, Luigi; Lupi, Luca; Vaselli, Orlando; Polonia, Alina; Gasperini, Luca

    2017-05-01

    The boundary between the African and Arabian plates in the Southern Red Sea region is displaced inland in the northern Afar rift, where it is marked by the Red Sea-parallel Erta Ale, Alaita, and Tat Ali volcanic ridges. The Erta Ale is offset by about 20 and 40 km from the two en echelon ridges to the south. The offset area is highly seismic and marked by a depression filled by lake Afrera, a saline body of water fed by hydrothermal springs. Acoustic bathymetric profiles show ≈80 m deep canyons parallel to the NNW shore of the lake, part of a system of extensional normal faults striking parallel to the Red Sea. This system is intersected by oblique structures, some with strike-slip earthquakes, in what might evolve into a transform boundary. Given that the lake's surface lies today about 112 m below sea level, the depressed (minus ≈190 m below sea level) lake's bottom area may be considered the equivalent of the "nodal deep" in slow-slip oceanic transforms. The chemistry of the lake is compatible with the water having originated from hydrothermal liquids that had reacted with evaporites and basalts, rather than residual from evaporation of sea water. Bottom sediments include calcitic grains, halite and gypsum, as well as ostracod and diatom tests. The lake's level appears to have dropped by over 10 m during the last ≈50 years, continuing a drying up trend of the last few thousand years, after a "wet" stage 9,800 and 7,800 years before present when according to Gasse (1973) Lake Afrera covered an area several times larger than at present. This "wet" stage corresponds to an early Holocene warm-humid climate that prevailed in Saharan and Sub Saharan Africa. Lake Abhé, located roughly 250 km south of Afrera, shows similar climate-driven oscillations of its level.

  11. Discovery of relict subglacial lakes and their geometry and mechanism of drainage

    PubMed Central

    Livingstone, Stephen J.; Utting, Daniel J.; Ruffell, Alastair; Clark, Chris D.; Pawley, Steven; Atkinson, Nigel; Fowler, Andrew C.

    2016-01-01

    Recent proxy measurements reveal that subglacial lakes beneath modern ice sheets periodically store and release large volumes of water, providing an important but poorly understood influence on contemporary ice dynamics and mass balance. This is because direct observations of how lake drainage initiates and proceeds are lacking. Here we present physical evidence of the mechanism and geometry of lake drainage from the discovery of relict subglacial lakes formed during the last glaciation in Canada. These palaeo-subglacial lakes comprised shallow (<10 m) lenses of water perched behind ridges orientated transverse to ice flow. We show that lakes periodically drained through channels incised into bed substrate (canals). Canals sometimes trend into eskers that represent the depositional imprint of the last high-magnitude lake outburst. The subglacial lakes and channels are preserved on top of glacial lineations, indicating long-term re-organization of the subglacial drainage system and coupling to ice flow. PMID:27292049

  12. Organizational Citizenship Levels of Academicians in Terms of Several Variables: The Sample of Physical Education and Sports Sciences

    ERIC Educational Resources Information Center

    Aydin, Ali Dursun

    2015-01-01

    This study is performed with 176 academicians working in the institutions related to physical education and sports at universities. It aims to analyze organizational citizenship behaviours of academic personnel about the institutions they have been working in. Descriptive survey model was used, along with demographic data like gender, marital…

  13. Optically stimulated luminescence dating of late Holocene raised strandplain sequences adjacent to Lakes Michigan and Superior, Upper Peninsula, Michigan, USA

    USGS Publications Warehouse

    Argyilan, Erin P.; Forman, Steven L.; Johnston, John W.; Wilcox, Douglas A.

    2005-01-01

    This study evaluates the accuracy of optically stimulated luminescence to date well-preserved strandline sequences at Manistique/Thompson bay (Lake Michigan), and Tahquamenon and Grand Traverse Bays (Lake Superior) that span the past ∼4500 yr. The single aliquot regeneration (SAR) method is applied to produce absolute ages for littoral and eolian sediments. SAR ages are compared against AMS and conventional 14C ages on swale organics. Modern littoral and eolian sediments yield SAR ages 14C ages on swale organics. Significant variability in 14C ages >2000 cal yr B.P. complicates comparison to SAR ages at all sites. However, a SAR age of 4280 ± 390 yr (UIC913) on ridge77 at Tahquamenon Bay is consistent with regional regression from the high lake level of the Nipissing II phase ca. 4500 cal yr B.P. SAR ages indicate a decrease in ridge formation rate after ∼1500 yr ago, likely reflecting separation of Lake Superior from lakes Huron and Michigan. This study shows that SAR is a credible alternative to 14C methods for dating littoral and eolian landforms in Great Lakes and other coastal strandplains where 14C methods prove problematic.

  14. [Academician Li Lianda talking about doctors doing scientific research].

    PubMed

    He, Ping; Li, Yi-kui

    2015-09-01

    At present, Chinese medical field faces with an important problem of how to correctly handle the relationship between medical and scientific research. Academician Li Lianda advocates doctors doing scientific research under the premise of putting the medical work first. He points out that there are many problems in the process of doctors doing scientific research at present such as paying more attention to scientific research than medical care, excessively promoting building scientific research hospital, only paying attention to training scientific talents, research direction be flashy without substance, the medical evaluation system should be improved and so on. Medical, scientific research and teaching are inseparable because improving medical standards depends on scientific research and personnel training. But not all doctors need to take into account of medical treatment, scientific research and teaching in the same degree while not all hospitals need to turn into three-in-one hospital, scientific research hospital or teaching hospital. It must be treated differently according to the actual situation.

  15. Hotspot-Ridge Interaction: Shaping the Geometry of Mid-Ocean Ridges

    NASA Astrophysics Data System (ADS)

    Mittelstaedt, E.; Ito, G.

    2004-12-01

    Surface manifestations of hotspot-ridge interaction include geochemical anomalies, elevated ridge topography, negative gravity anomalies, off-axis volcanic lineaments, and ridge reorganization events. The last of these is expressed as either "captured" ridge segments due to asymmetric spreading, such as at the Galapagos, or as discrete jumps of the ridge axis toward the hotspot, such as at the Iceland, Tristan de Cuhna, Discovery, Shona, Louisville, Kerguelen, and Reunion hotspots. Mid-ocean ridge axis reorganizations through discrete jumps will cause variations in local volcanic patterns, lead to changes in overall plate shape and ridge axis morphology, and alter local mantle flow patterns. It has been proposed that discrete ridge jumps are a product of interaction between the lithosphere and a mantle plume. We examine this hypothesis using thin plate theory coupled with continuum damage mechanics to calculate the two-dimensional (plan-view) pattern of depth-integrated stresses in a plate of varying thickness with weakening due to volcanism at the ridge and above the plume center. Forces on the plate include plume shear, plate parallel gravitational forces due to buoyant uplift, and a prescribed velocity of plate motion along the edges of the model. We explore these forces and the effect of damage as mechanisms that may be required to predict ridge jumps.

  16. Ice-walled-lake plains: Implications for the origin of hummocky glacial topography in middle North America

    USGS Publications Warehouse

    Clayton, L.; Attig, J.W.; Ham, N.R.; Johnson, M.D.; Jennings, C.E.; Syverson, K.M.

    2008-01-01

    Ice-walled-lake plains are prominent in many areas of hummocky-till topography left behind as the Laurentide Ice Sheet melted from middle North America. The formation of the hummocky-till topography has been explained by: (1) erosion by subglacial floods; (2) squeezing of subglacial till up into holes in stagnant glacial ice; or (3) slumping of supraglacial till. The geomorphology and stratigraphy of ice-walled-lake plains provide evidence that neither the lake plains nor the adjacent hummocks are of subglacial origin. These flat lake plains, up to a few kilometers in diameter, are perched as much as a few tens of meters above surrounding depressions. They typically are underlain by laminated, fine-grained suspended-load lake sediment. Many ice-walled-lake plains are surrounded by a low rim ridge of coarser-grained shore sediment or by a steeper rim ridge of debris that slumped off the surrounding ice slopes. The ice-walled lakes persisted for hundreds to thousands of years following glacial stagnation. Shells of aquatic molluscs from several deposits of ice-walled-lake sediment in south-central North Dakota have been dated from about 13 500 to 10 500??B.P. (calibrated radiocarbon ages), indicating a climate only slightly cooler than present. This is confirmed by recent palaeoecological studies in nearby non-glacial sites. To survive so long, the stagnant glacial ice had to be well-insulated by a thick cover of supraglacial sediment, and the associated till hummocks must be composed primarily of collapsed supraglacial till. ?? 2007 Elsevier B.V. All rights reserved.

  17. The Distribution of Antarctic Subglacial Lake Environments With Implications for Their Origin and Evolution

    NASA Astrophysics Data System (ADS)

    Blankenship, D. D.; Young, D. A.; Carter, S. P.

    2006-12-01

    Ice-penetrating radar records across the Antarctic Ice Sheet show regions with strong flat mirror-like reflections from the subglacial interface that are interpreted to be from subglacial lakes. The majority of subglacial lakes are found in East Antarctica, primarily in topographically low areas of basins beneath the thick ice divides. Occasionally lakes are observed "perched" at higher elevations within local depressions of rough morphological regions. In addition, a correlation between the "onset" of enhanced glacial flow and subglacial lakes was identified. The greatest concentration of known lakes was found in the vicinity of Dome C. A second grouping of lakes lying near Ridge B includes Lake Vostok and several smaller lakes. Subglacial lakes were also discovered near the South Pole, within eastern Wilkes Land, west of the Transantarctic Mountains, and within West Antarctica's Whitmore Mountains. Aside from Lake Vostok, typical lengths of subglacial lakes were found to range from a few to about 20 kilometers. A recent inventory includes 145 subglacial lakes. Approximately 81% of detected lakes lie at elevations less than a few hundred meters above sea level while the majority of the remaining lakes are "perched" at higher elevations. We present the locations from the subglacial lake inventory on local "ice divides" calculated from the satellite derived surface elevations with and find the distance of each lake from these divides. Most significantly, we found that 66% of the lakes identified lie within 50 km of a local ice divide and 88% lie within 100 km of a local divide. In particular, note that lakes located far from the Dome C/Ridge B cluster and even those associated with very narrow catchments lie either on or within a few tens of kilometers of the local divide marked by the catchment boundary. The distance correlation of subglacial lakes with local ice divides leads to a fundamental question for the evolution of subglacial lake environments: Does the

  18. Reconstructing Environmental Change Using Lake Varves as a Climate Proxy

    ERIC Educational Resources Information Center

    Dempsey, Christopher; Bodzin, Alec; Cirucci, Lori; Anastasio, David; Sahagian, Dork

    2012-01-01

    In this article, the authors describe an investigative activity in which their eighth-grade students reconstructed past environmental change in the New England area using data from lake varves in central Vermont to examine evidence of climate change. The investigation uses an authentic paleoclimate record (Ridge 2011) from the Pleistocene epoch,…

  19. Oak Ridge Reservation Physical Characteristics and Natural Resources

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Parr, P.D.; Hughes, J.F.

    The topography, geology, hydrology, vegetation, and wildlife of the Oak Ridge Reservation (ORR) provide a complex and intricate array of resources that directly impact land stewardship and use decisions (Fig. 1). The purpose of this document is to consolidate general information regarding the natural resources and physical characteristics of the ORR. The ORR, encompassing 33,114 acres (13,401 ha) of federally owned land and three Department of Energy (DOE) installations, is located in Roane and Anderson Counties in east Tennessee, mostly within the corporate limits of the city of Oak Ridge and southwest of the population center of Oak Ridge. Themore » ORR is bordered on the north and east by the population center of the city of Oak Ridge and on the south and west by the Clinch River/Melton Hill Lake impoundment. All areas of the ORR are relatively pristine when compared with the surrounding region, especially in the Valley and Ridge Physiographic Province (Fig. 2). From the air, the ORR is clearly a large and nearly continuous island of forest within a landscape that is fragmented by urban development and agriculture. Satellite imagery from 2006 was used to develop a land-use/land-cover cover map of the ORR and surrounding lands (Fig. 3). Following the acquisition of the land comprising the ORR in the early 1940s, much of the Reservation served as a buffer for the three primary facilities: the X-10 nuclear research facility (now known as the Oak Ridge National Laboratory [ORNL]), the first uranium enrichment facility or Y-12 (now known as the Y-12 National Security Complex [Y-12 Complex]), and a gaseous diffusion enrichment facility (now known as the East Tennessee Technology Park [ETTP]). Over the past 60 years, this relatively undisturbed area has evolved into a rich and diverse eastern deciduous forest ecosystem of streams and reservoirs, hardwood forests, and extensive upland mixed forests. The combination of a large land area with complex physical

  20. Ridge: a computer program for calculating ridge regression estimates

    Treesearch

    Donald E. Hilt; Donald W. Seegrist

    1977-01-01

    Least-squares coefficients for multiple-regression models may be unstable when the independent variables are highly correlated. Ridge regression is a biased estimation procedure that produces stable estimates of the coefficients. Ridge regression is discussed, and a computer program for calculating the ridge coefficients is presented.

  1. Late Pleistocene to Holocene lake levels of Lake Warner, Oregon (USA) and their effect on archaeological site distribution patterns

    NASA Astrophysics Data System (ADS)

    Wriston, T.; Smith, G. M.

    2017-12-01

    Few chronological controls are available for the rise and fall of small pluvial lake systems in the Northwestern Great Basin. Within Warner Basin this control was necessary for interpretation of known archaeological sites and for predicting where evidence of its earliest inhabitants might be expected. We trenched along relic beach ridges of Lake Warner, surveyed a stratified sample of the area for archaeological sites, and excavated some sites and a nearby rockshelter. These efforts produced new ages that we used to construct a lake level curve for Lake Warner. We found that the lake filled the valley floor between ca. 30,000 cal yr BP and ca. 10,300 cal yr BP. In nearby basins, several oscillations are evident before ca. 21,100 cal yr BP, but a steep rise to the LGM maximum occurred between 21,000 and 20,000 cal yr BP. Lake Warner likely mirrored these changes, dropped to the valley floor ca. 18,340 cal yr BP, and then rose to its maximum highstand when its waters briefly reached 1454 m asl. After this highstand the lake receded to moderately high levels. Following ca. 14,385 cal yr BP, the lake oscillated between moderate to moderately-high levels through the Bolling-Allerod interstadials and into the Younger Dryas stadial. The basin's first occupants arrived along its shore around this time, while the lake still filled the valley floor. These earliest people carried either Western Stemmed or Clovis projectile points, both of which are found along the lake margin. The lake receded into the valley floor ca. 10,300 cal yr BP and dune development began, ringing wetlands and small lakes that persisted in the footprint of the once large lake. By the time Mazama tephra fell 7,600 cal yr BP it blanketed pre-existing dunes and marsh peats. Our Lake Warner lake level curve facilitates interdisciplinary testing and refinement of it and similar curves throughout the region while helping us understand the history of lake and the people who lived along its shores.

  2. Volcanic/Tectonic Characteristics of First and Second Order Segments and Ridge Discontinuities `Under the Hot-spot Influence' - TOBI Imagery from the Central Indian Ridge (CIR) Adjacent to the Rodriguez System.

    NASA Astrophysics Data System (ADS)

    Parson, L.; Murton, B.; Sauter, D.; Curewitz, D.; Okino, K.; German, C.; Leven, J.

    2001-12-01

    Deeptow sidescan sonar data (TOBI, 30kHz) acquired over more than 200 km of the Central Indian Ridge during RRS Charles Darwin cruise CD127 reveal an abundance of neovolcanic activity throughout both spreading segments and ridge non-transform discontinuities alike. Imagery of the previously unsurveyed northern section of the CIR immediately south of the Marie Celeste Fracture Zone confirms the presence of a shallow, magmatically inflated second order segment that is only recently rifted, with a rift floor surfaced throughout by virtually untectonised planar sheet flow units. First and second order segments exhibit a significant component of sheeted extrusives, ponded or in lake form, abutting or overstepped by hummocky and mounded pillow constructs. Non-transform discontinuities are commonly cut by fresh axial volcanic ridges oblique to both axial trend and offset. The depths of segment centers range from 2600m to more than 3700m, and segment forms include robust, hour-glass and rifted/starved end-members - but their overall extrusive pattern is strikingly invariant. Fracture Zone offsets of up to 65 kilometres are tectonically dominated, but their intersections with the axis are often mantled by multiple sheet flows rather than the relatively low proportions of sediment cover. The largest offsets are marked by outcrops of multiple, subparallel displacement surfaces, actively eroding transverse ridges, and ridge transform intersections with classic propagation/recession fabrics - each suggesting some instability in regional plate kinematics. While it is tempting to speculate that the Rodrigues hotspot appears to have a regional effect, enhancing magmatic delivery to the adjacent ridge and offset system, the apparent breadth of influence from what is assumed to be a rather feeble mantle anomaly is problematic.

  3. Summit Lake landslide and geomorphic history of Summit Lake basin, northwestern Nevada

    USGS Publications Warehouse

    Curry, B. Brandon; Melhorn, W.N.

    1990-01-01

    The Summit Lake landslide, northwestern Nevada, composed of Early Miocene pyroclastic debris, Ashdown Tuff, and basalt and rhyolite of the Black Rock Range, blocked the upper Soldier Creek-Snow Creek drainage and impounded Summit Lake sometimes prior to 7840 yr B.P. The slide covers 8.2 km2 and has geomorphic features characteristic of long run-out landslides, such as lobate form, longitudinal and transverse ridges, low surface gradient (7.1 ??), and preservation of original stratigraphic position of transported blocks. However, estimated debris volume is the smallest reported (2.5 ?? 105 m3) for a landslide of this type. The outflow channel of the Summit Lake basin was a northward-flowing stream valley entrenched by Mahogany Creek. Subsequent negative tectonic adjustment of the basin by about 35 m, accompanied by concommitant progradation of a prominent alluvial fan deposited by Mahogany Creek, argues for a probable diversion of drainage from the Alvord basin southward into the Lahontan basin. The landslide occurred while the creek flowed southward, transferring about 147 km2 of watershed from the Lahontan basin back to the Alvord basin. Overflow northward occurred during high stands of Pluvial Lake Parman in the basin; otherwise, under drier climates, the Summit Lake basin has been closed. Within large depressions on the slide surface, the ca. 6800 yr old Mazama Bed and other sediments have buried a weakly developed soil. Disseminated humus in the soil yields an age of 7840 ?? 310 yr B.P. Absence of older tephra (such as St. Helens M) brackets the slide age between 7840 and 19,000 yr B.P. Projectile points found on the highest strandlines of Pluvial Lake Parman suggest a ca 8700 yr B.P. age by correlation with cultural artifacts and radiocarbon ages from nearby Last Supper Cave, Nevada. Organic matter accumulation in landslide soils suggests ages ranging from 9100 to 16,250 yr B.P. Estimation of the age of the slide from morphologic data for the isolated Summit

  4. The importance of Leonhard Euler's discoveries in the field of shipbuilding for the scientific evolution of academician A. N. Krylov

    NASA Astrophysics Data System (ADS)

    Sharkov, N. A.; Sharkova, O. A.

    2018-05-01

    The paper identifies the importance of the Leonhard Euler's discoveries in the field of shipbuilding for the scientific evolution of academician A. N. Krylov and for the modern knowledge in survivability and safety of ships. The works by Leonard Euler "Marine Science" and "The Moon Motion New Theory" are discussed.

  5. Geological setting of the Concordia Trench-Lake system in East Antarctica

    NASA Astrophysics Data System (ADS)

    Cianfarra, P.; Forieri, A.; Salvini, F.; Tabacco, I. E.; Zirizotti, A.

    2009-06-01

    This study presents the interpretation of radio echo-sounding (RES) data collected during the 2003 geophysical campaign of PNRA (Italian National Research Project in Antarctica), which focused on the exploration of the Concordia Trench-Lake system in East Antarctica. The data allow us to identify a new lake (ITL-28) at the southern edge of the Concordia Trench and a series of N-S trending subglacial troughs cutting through the Belgica Highlands. We have mapped the bedrock morphology at 3 km resolution, which led to an improved geographical and geomorphological characterization of the Concordia Trench, Concordia Ridge, Concordia Lake and South Hills. Improved knowledge of the Concordia Trench allowed us to model the 3-D geometry of the Concordia fault, suggesting that it played a role in governing the morpho-tectonic evolution of the bedrock in the Dome C region, and to propose a Cenozoic age for its activity. We recognize the importance of catchment basin morphology in hosting subglacial lakes, and discuss the role played by tectonics, glacial scouring and volcanism in the origin of the trench lakes, basin lakes and relief lakes, respectively.

  6. Ridge of Jagged Peaks on Titan

    NASA Image and Video Library

    2016-07-29

    This synthetic-aperture radar image was obtained by NASA's Cassini spacecraft during its T-120 pass over Titan's southern latitudes on June 7, 2016. The area shown here measures about 40 by 60 miles (70 by 100 kilometers) and is centered at about 60 degrees south latitude, 130 degrees west longitude. Radar illuminates the scene from the left at a 28-degree incidence angle. At the center of the image is a bright feature oriented from upper left to lower right. This is interpreted to be a long ridge with jagged peaks, likely created by methane rainfall erosion. Some of the individual peaks rise about 2,400 feet (800 meters) above the valley floor. The ridge has a considerably gentler slope on its left side (which appears brighter here) than on its right. Frequently, mountains shaped like this on Earth are fractured blocks of the planet's crust, thrusted upward and then tilted, creating a shallow slope on one side and a steeper slope on the fractured, faulted edge. Also presented here is an annotated version of the image, along with a radar image of the Dragoon Mountains in Arizona just east of Tucson. The Dragoon feature represents a tilted fault block, formed by spreading that has occurred across the western U.S., and has a similar shape to that of the Titan ridge. The Dragoon radar image was produced using data from NASA's Shuttle Radar Topography Mission (credit: NASA/JPL-Caltech/NGA). Radar illuminates the scene from the left in that image as well. Titan has displayed many features that are strikingly similar to Earth: lakes, seas, rivers, dunes and mountains. Scientists think it possible that, like Earth, the giant moon's crust has experienced familiar processes of uplift and spreading, followed by erosion. http://photojournal.jpl.nasa.gov/catalog/PIA20709

  7. Lasting Effects of Glacial Lake Outburst Floods on Subglacial Drainage Networks

    NASA Astrophysics Data System (ADS)

    Robbins, M.; Hendy, I. L.; Bassis, J. N.; Aciego, S.; Stevenson, E. I.

    2017-12-01

    Supraglacial lakes forming in the ablation zone around the Greenland Ice Sheet will likely migrate toward higher elevations as polar temperatures rise through the 21st century. Present understanding of lake drainage shows it can temporarily enhance ice sheet motion, but other possible effects and interactions - especially with older pre-existing subglacial reservoirs - remain unexamined. Here we investigate possible enduring effects of the record high 2012 melt year on the en/subglacial hydrologic network, how this network responds to immediate high fluxes of water from floods, and how these phenomena might connect to previously isolated subglacial pools. Lake Hullet is a large ice dammed lake situated in south Greenland 22km up-ice from where Kiattuut Sermiat (KS) branches from a larger outlet glacier. Lake Hullet rests on bedrock and is contained by a bedrock ridge. It drains roughly annually through Lake Hullet's hydrologic network in a glacial lake outburst flood (GLOF) when water level rises such that it can flow over the obstructive ridge. Subglacial water samples collected from the toe of KS in July 2013 pre-flood were dated using U isotopes with 222Rn concentrations as well as noble gas ratios. These two independent methods reveal an exceedingly old water age of > 1000 years, indicating existence of isolated enduring subglacial meltwater pool(s). A comparison field study at the KS toe in August and September 2015 re-examined glacial hydrochemistry in a time series. 2015 222Rn concentrations are lower than 2013 values, suggesting less water-rock interaction, a reduction in residence time, and a proximal meltwater source. Increased water volume from the record high 2012 melt year may have enlarged the existing en/subglacial drainage network further into the ice sheet releasing meltwater with longer residence times beneath the ice, with effects lasting into subsequent melt seasons due to the stability of channels maintained from recurrent floods. These

  8. Bird mortality associated with wind turbines at the Buffalo Ridge wind resource area, Minnesota

    USGS Publications Warehouse

    Osborn, R.G.; Higgins, K.F.; Usgaard, R.E.; Dieter, C.D.; Neiger, R.D.

    2000-01-01

    Recent technological advances have made wind power a viable source of alternative energy production and the number of windplant facilities has increased in the United States. Construction was completed on a 73 turbine, 25 megawatt windplant on Buffalo Ridge near Lake Benton, Minnesota in Spring 1994. The number of birds killed at existing windplants in California caused concern about the potential impacts of the Buffalo Ridge facility on the avian community. From April 1994 through Dec. 1995 we searched the Buffalo Ridge windplant site for dead birds. Additionally, we evaluated search efficiency, predator scavenging rates and rate of carcass decomposition. During 20 mo of monitoring we found 12 dead birds. Collisions with wind turbines were suspected for 8 of the 12 birds. During observer efficiency trials searchers found 78.8% of carcasses. Scavengers removed 39.5% of carcasses during scavenging trials. All carcasses remained recognizable during 7 d decomposition trials. After correction for biases we estimated that approximately 36 ?? 12 birds (<1 dead bird per turbine) were killed at the Buffalo Ridge windplant in 1 y. Although windplants do not appear to be more detrimental to birds than other man-made structures, proper facility sitting is an important first consideration in order to avoid unnecessary fatalities.

  9. Ridge Tectonics, Magma Supply, and Ridge-Hotpot Interaction at the Eastern End of the Australian-Antarctic Ridge

    NASA Astrophysics Data System (ADS)

    Kim, S.; Lin, J.; Park, S.; Choi, H.; Lee, S.

    2013-12-01

    During 2011-2013 the Korea Polar Research Institute (KOPRI) conducted three successive expeditions to the eastern end of the Australian-Antarctic Ridge (AAR) to investigate the tectonics, geochemistry, and hydrothermal activity of this intermediate fast spreading system. On board the Korean icebreaker R/V Araon, the science party collected multiple types of data including multibeam bathymetry, gravity, magnetics, as well as rock and water column samples. In addition, Miniature Autonomous Plume Recorders (MAPRs) were deployed at each of the wax-core rock sampling sites to detect the presence of active hydrothermal vents. In this study, we present a detailed analysis of a 360-km-long super-segment at the eastern end of the AAR to quantify the spatial variations in ridge morphology and investigate its respond to changes in melt supply. The study region contains several intriguing bathymetric features including (1) abrupt changes in the axial topography, alternating between rift valleys and axial highs within relatively short ridge segments; (2) overshooting ridge tips at the ridge-transform intersections; (3) systematic migration patterns of hooked ridges; (4) a 350-km-long mega-transform fault; and (5) robust axial and off-axis volcanisms. To obtain a proxy for regional variations in magma supply, we calculated residual mantle Bouguer gravity anomalies (RMBA), gravity-derived crustal thickness, and residual topography for seven sub-segments. The results of the analyses revealed that the southern flank of the AAR is associated with a shallower seafloor, more negative RMBA, thicker crust, and/or less dense mantle than the conjugate northern flank. Furthermore, this N-S asymmetry becomes more prominent toward the super-segment of the AAR. Such regional variations in seafloor topography and RMBA are consistent with the hypothesis that ridge segments in the study area have interacted with the Balleny hotspot, currently lies southwest of the AAR. However, the influence of

  10. Mercury in wetlands at the Glacial Ridge National Wildlife Refuge, northwestern Minnesota, 2007-9

    USGS Publications Warehouse

    Cowdery, Timothy K.; Brigham, Mark E.

    2013-01-01

    The Glacial Ridge National Wildlife Refuge was established in 2004 on land in northwestern Minnesota that had previously undergone extensive wetland and prairie restorations. About 7,000 acres of drained wetlands were restored to their original hydrologic function and aquatic ecosystem. During 2007–9, the U.S. Geological Survey, in cooperation with the U.S. Fish and Wildlife Service and the Red Lake Watershed District, analyzed mercury concentrations in wetland water and sediment to evaluate the effect of wetland restoration on mercury methylation. The wetland waters sampled generally were of the calcium/magnesium bicarbonate type. Nitrogen in water was mostly in the form of dissolved-organic nitrogen, with very low dissolved-nitrate and dissolved-ammonia concentrations. About 71 percent of all phosphorus in water was dissolved, with one-half of that in the form of orthophosphorus. Wetland water had total-mercury and methylmercury concentrations ranging from 1.5 to 20 nanograms per liter (ng/L) and 0.2 to 16 ng/L, respectively. Median concentrations were 7.1 and 2.9 ng/L, respectively. About one-half of the mercury in wetland water samples was in the form of methylmercury, but this form ranged from 7 to 81 percent of each sample. Compared to concentrations in stream sediment samples collected throughout the United States, Glacial Ridge National Wildlife Refuge wetland sediment samples contained typical total-mercury concentrations, but methylmercury concentrations were nearly twice as high. The maximum concentration measured in Glacial Ridge National Wildlife Refuge wetland water approached the highest published water methylmercury concentration in uncontaminated waters of which we are aware. However, the upper quartile of water methylmercury concentrations is similar to concentrations reported for some impoundments and wetlands in northwestern Minnesota and North Dakota. Methylmercury concentrations in sampled wetlands were much higher than those from typical

  11. Polygonal ridge networks on Mars: Diversity of morphologies and the special case of the Eastern Medusae Fossae Formation

    NASA Astrophysics Data System (ADS)

    Kerber, Laura; Dickson, James L.; Head, James W.; Grosfils, Eric B.

    2017-01-01

    Polygonal ridge networks, also known as boxwork or reticulate ridges, are found in numerous locations and geological contexts across Mars. Distinguishing the morphologies and geological context of the ridge networks sheds light on their potential as astrobiological and mineral resource sites of interest. The most widespread type of ridge morphology is characteristic of the Nili Fossae and Nilosyrtis region and consists of thin, criss-crossing ridges with a variety of heights, widths, and intersection angles. They are found in ancient Noachian terrains at a variety of altitudes (between -2500 and 2200 m) and geographic locations and are likely to be chemically altered fracture planes or mineral veins. They occur in the same general areas as valley networks and ancient lake basins, but they are not more numerous where these water-related features are concentrated, and can appear in places where th morphologies are absent. Similarly, some of the ridge networks are located near hydrated mineral detections, but there is not a one-to-one correlation. Smaller, light-toned ridges of variable widths have been found in Gale Crater and other rover sites and are interpreted to be smaller versions of the Nili-like ridges, mostly formed by the mineralization of fractures. This type of ridge is likely to be found in many other places on Mars as more high-resolution data become available. Sinus Meridiani contains many flat-topped ridges arranged into quasi-circular patterns. The ridges are eroding from a clay-rich unit, and could be formed by a similar process as the Nili-type ridges, but at a much larger scale and controlled by fractures made through a different process. Hellas Basin is host to a fourth type of ridge morphology consisting of large, thick, light-toned ridges forming regular polygons at several superimposed scales. While still enigmatic, these are most likely to be the result of sediment-filled fractures. The Eastern Medusae Fossae Formation contains large swaths

  12. Channel Networks on Large Fans: Refining Analogs for the Ridge-forming Unit, Sinus Meridiani

    NASA Technical Reports Server (NTRS)

    Wilkinson, Justin

    2009-01-01

    Stream channels are generally thought of as forming within confined valley settings, separated by interfluves. Sinuous ridges on Mars and Earth are often interpreted as stream channels inverted by subsequent erosion of valley sides. In the case of the ridge-forming unit (RFU), this interpretation fails to explain the (i) close spacing of the ridges, which are (ii) organized in networks, and which (iii) cover large areas (approximately 175,000 km (exp 2)). Channel networks on terrestrial fans develop unconfined by valley slopes. Large fans (100s km long) are low-angle, fluvial features, documented worldwide, with characteristics that address these aspects of the RFU. Ridge patterns Channels on large fans provide an analog for the sinuous and elongated morphology of RFU ridges, but more especially for other patterns such as subparallel, branching and crossing networks. Branches are related to splays (delta-like distributaries are rare), whose channels can rejoin the main channel. Crossing patterns can be caused by even slight sinuosity splay-related side channels often intersect. An avulsion node distant from the fan apex, gives rise to channels with slightly different, and hence intersecting, orientations. Channels on neighboring fans intersect along the common fan margin. 2. Network density Channels are the dominant feature on large terrestrial fans (lakes and dune fields are minor). Inverted landscapes on subsequently eroded fans thus display indurated channels as networks of significantly close-spaced ridges. 3. Channel networks covering large areas Areas of individual large terrestrial fans can reach >200,000 km 2 (105-6 km 2 with nested fans), providing an analog for the wide area distribution of the RFU.

  13. Wind-driven Water Bodies : a new paradigm for lake geology

    NASA Astrophysics Data System (ADS)

    Nutz, A.; Schuster, M.; Ghienne, J. F.; Roquin, C.; Bouchette, F. A.

    2015-12-01

    In this contribution we emphasize the importance in some lakes of wind-related hydrodynamic processes (fair weather waves, storm waves, and longshore, cross-shore and bottom currents) as a first order forcing for clastics remobilization and basin infill. This alternative view contrasts with more classical depositional models for lakes where fluvial-driven sedimentation and settling dominates. Here we consider three large lakes/paleo-lakes that are located in different climatic and geodynamic settings: Megalake Chad (north-central Africa), Lake Saint-Jean (Québec, Canada), and Lake Turkana (Kenya, East African Rift System). All of these three lake systems exhibit well developed modern and ancient high-energy littoral morphosedimentary structures which directly derive from wind-related hydrodynamics. The extensive paleo-shorelines of Megalake Chad are composed of beach-foredune ridges, spits, wave-dominated deltas, barriers, and wave-ravinment surface. For Lake Saint-Jean the influence of wind is also identified below the wave-base at lake bottom from erosional surfaces, and sediment drifts. In the Lake Turkana Basin, littoral landforms and deposits are identified for three different time intervals (today, Holocene, Plio-Pleistocene) evidencing that wind-driven hydrodynamics can be preserved in the geological record. Moreover, a preliminary global survey suggests that numerous modern lakes (remote sensing) and paleo-lakes (bibliographic review) behave as such. We thus coin the term "Wind-driven Water Bodies" (WWB) to refer to those lake systems where sedimentation (erosion, transport, deposition) is dominated by wind-induced hydrodynamics at any depth, as it is the case in the marine realm for shallow seas. Integrating wind forcing in lake models has strong implications for basin analysis (paleoenvironments and paleoclimates restitutions, resources exploration), but also for coastal engineering, wildlife and reservoirs management, or leisure activities.

  14. Views of Academicians, School Administrators, and Teachers Regarding the Use of E-Portfolios in Transition from Elementary Education to Secondary Education

    ERIC Educational Resources Information Center

    Ada, Sibel; Tanberkan Suna, Hande; Elkonca, Fuat

    2016-01-01

    The general purpose of this study is to determine the views of academicians, school administrators, and teachers regarding the effects that can emerge from the use of e-portfolios as alongside the central joint exam in the transition from elementary education to secondary education. This research is a case study type from among the qualitative…

  15. Eskers in Ireland, analogs for sinuous ridges on Mars

    NASA Astrophysics Data System (ADS)

    Pellicer, Xavier; Bourke, Mary

    2014-05-01

    resolution images also show the presence of large boulders. Large glacial lakes in the Irish Midlands during ice withdrawal aided the outstanding preservation of these features. This permitted the cataloguing of 'pristine' morphologies and morphometries. Esker-like ridges identified on Mars are often located in low relief and depressions and show similar topographic conditions to those in Ireland. The ExoMars rover scheduled to be launched on the surface of Mars by 2018 carries the first space-borne GPR system (Wisdom) with the objective of characterizing the top 3 m of the Martian subsurface. Ground Penetrating Radar (GPR) surveys carried out on the Irish eskers and associated sediments depicted the landforms internal architecture and paleocurrent indicators. A throughout investigation of the Irish eskers as Mars analogs using remote sensing methods and GPR will contribute to the understanding of sinuous ridges on Mars.

  16. Remedial Investigation Work Plan for Chestnut Ridge Operable Unit 1 (Chestnut Ridge Security Pits) at the Oak Ridge Y-12 Plant, Oak Ridge, Tennessee

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Not Available

    1994-03-01

    This document outlines the activities necessary to conduct a Remedial Investigation (RI) of the Chestnut Ridge Security Pits (CRSP) at the Oak Ridge Y-12 Plant. The CRSP, also designated Chestnut Ridge Operable Unit (OU) 1, is one of four OUs along Chestnut Ridge on the Oak Ridge Reservation (ORR). The purpose of the RI is to collect data to (1) evaluate the nature and extent of known and suspected contaminants, (2) support an Ecological Risk Assessment (ERA) and a Human Health Risk Assessment (HHRA), (3) support the feasibility study in the development and analysis of remedial alternatives, and (4) ultimately,more » develop a Record of Decision (ROD) for the site. This chapter summarizes the regulatory background of environmental investigation on the ORR and the approach currently being followed and provides an overview of the RI to be conducted at the CRSP. Subsequent chapters provide details on site history, sampling activities, procedures and methods, quality assurance (QA), health and safety, and waste management related to the RI.« less

  17. Anatomy of the Midcontinent Rift beneath Lake Superior

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Thompson, M.D.; McGinnis, L.D.; Ervin, C.P.

    1994-09-01

    The structure and geometry of the 1.1-b.y.-old Midcontinent Rift system under Lake Superior is interpreted from 20 seismic reflection profiles recorded during the early and mid-1980s. The seismic data reveal that rift basins under Lake Superior are variable in depth and are partially filled with Keweenawan age sediments to depths of 7 km or more and volcanic flows to depths of 36 km. These rift basins form a continuous and sinuous feature that widens in the Allouez Basin and Marquette Basin in the western and central lake and narrows between White Ridge and the Porcupine Mountains. The rift basin bendsmore » southeast around the Keweenaw Peninsula, widens to about 100 km as it extends into the eastern half of Lake Superior, and exists the lake with its axis in the vicinity of Au Sable Point in Pictured Rocks National Lake Shore, about 50 km northeast of Munising, Michigan. The axis of the rift may exit the western end of the lake near Chequamegon Bay in Wisconsin. However, lack of data in that area limits interpretation at this time. Prior to late-stage reverse-faulting, a continuous basin of more uniform thickness was present beneath the lake. Crustal extension during rifting of approximately 50 km was followed by plate convergence and crustal shortening of approximately 30 km, with the major component of thrust from the southeast. Crustal shortening occurred after development of rift grabens and their filling with lava flows, but before deposition of the final sag basin sediments. Integration of information obtained from outcrops with data reported here indicates that the Lake Superior section of the rift is associated with as many as three major boundary faults.« less

  18. Large subglacial lakes in East Antarctica at the onset of fast-flowing ice streams.

    PubMed

    Bell, Robin E; Studinger, Michael; Shuman, Christopher A; Fahnestock, Mark A; Joughin, Ian

    2007-02-22

    Water plays a crucial role in ice-sheet stability and the onset of ice streams. Subglacial lake water moves between lakes and rapidly drains, causing catastrophic floods. The exact mechanisms by which subglacial lakes influence ice-sheet dynamics are unknown, however, and large subglacial lakes have not been closely associated with rapidly flowing ice streams. Here we use satellite imagery and ice-surface elevations to identify a region of subglacial lakes, similar in total area to Lake Vostok, at the onset region of the Recovery Glacier ice stream in East Antarctica and predicted by ice-sheet models. We define four lakes through extensive, flat, featureless regions of ice surface bounded by upstream troughs and downstream ridges. Using ice velocities determined using interferometric synthetic aperture radar (InSAR), we find the onset of rapid flow (moving at 20 to 30 m yr(-1)) of the tributaries to the Recovery Glacier ice stream in a 280-km-wide segment at the downslope margins of these four subglacial lakes. We conclude that the subglacial lakes initiate and maintain rapid ice flow through either active modification of the basal thermal regime of the ice sheet by lake accretion or through scouring bedrock channels in periodic drainage events. We suggest that the role of subglacial lakes needs to be considered in ice-sheet mass balance assessments.

  19. Controls on melting at spreading ridges from correlated abyssal peridotite - mid-ocean ridge basalt compositions

    NASA Astrophysics Data System (ADS)

    Regelous, Marcel; Weinzierl, Christoph G.; Haase, Karsten M.

    2016-09-01

    Variations in the volume and major element composition of basalt erupted along the global mid-ocean ridge system have been attributed to differences in mantle potential temperature, mantle composition, or plate spreading rate and lithosphere thickness. Abyssal peridotites, the residues of mantle melting beneath mid-ocean ridges, provide additional information on the melting process, which could be used to test these hypotheses. We compiled a global database of abyssal peridotite compositions averaged over the same ridge segments defined by Gale et al. (2013). In addition, we calculated the distance of each ridge segment to the nearest hotspots. We show that Cr# in spinel in abyssal peridotites is negatively correlated with Na90 in basalts from the same ridge segments on a global scale. Ridge segments that erupt basalts apparently produced by larger degrees of mantle melting are thus underlain by peridotites from which large amounts of melt have been extracted. We find that near-ridge hotspots have a more widespread influence on mid-ocean ridge basalt (MORB) composition and ridge depth than previously thought. However, when these hotspot-influenced ridge segments are excluded, the remaining segments show clear relationships between MORB composition, peridotite composition, and ridge depth with spreading rate. Very slow-spreading ridges (<20 mm/yr) are deeper, erupt basalts with higher Na90, Al90, K90/Ti90, and lower Fe90, Ca90/Al90, and expose peridotites with lower Cr# than intermediate and fast-spreading ridges. We show that away from hotspots, the spreading-rate dependence of the maximum degree of mantle melting inferred from Cr# in peridotites (FM) and the bulk degree of melting inferred from Na90 in basalts (FB) from the same ridge segments is unlikely to be due to variations in mantle composition. Nor can the effects of dynamic mantle upwelling or incomplete melt extraction at low spreading rates satisfactorily explain the observed compositions of abyssal

  20. Assessment of the hydrologic interaction between Imikpuk Lake and the adjacent airstrip site near Barrow, Alaska, 1993

    USGS Publications Warehouse

    McCarthy, Kathleen A.; Solin, Gary L.; Trabant, Dennis

    1994-01-01

    Imikpuk Lake serves as the drinking water source for the Ukpeagvik Inupiat Corporation-National Arctic Research Laboratory (UIC-NARL), formerly known as the Naval Arctic Research Laboratory, near Barrow, Alaska. During the 1970's and 1980's, accidental releases of more than 1,300 cubic meters of various types of fuel occurred at the airstrip site adjacent to the lake. To aid an assessment of the potential risk 10 the quality of water in the lake posed by fuel remaining in the subsurface, the hydrologic interaction between the lake and ground water at the airstrip site was examined. The study area lies within the region of continuous permafrost where hydrologic processes are largely controlled by the short annual thaw season and the presence of near-surface permafrost. Runoff occurs for only a short period each year, typically from early or mid-June to late September, and a shallow ground- water system develops during approximately the same period as a result of shallow thawing of the subsurface. During the spring and summer of 1993, snowpack and surface-water data were collected throughout the Imikpuk Lake basin, and subsurface- flow-system data were collected at the airstrip site. The total annual inflow to the lake was estimated 10 be approximately 300,000 cubic meters per year, based on four methods of estimation. The ground-water flow system at the airstrip site is complex, primarily because of variations in local land-surface topography. Subsurface frost-elevation data indicate that a permafrost ridge exists beneath one of the elevated building pads at the site. Similar ridges beneath elevated roadways at the site may act as impediments to ground-water flow, reducing the flux of subsurface water to Imikpuk Lake. However, on the basis of the assumption that such impediments do not reduce flux substantially, the ground-water flux from the airstrip site was estimated to be approximately 173 cubic meters per year--less than 0.1 percent of the estimated annual

  1. Biomechanical comparison of a novel engine-driven ridge spreader and conventional ridge splitting techniques.

    PubMed

    Jung, Gyu-Un; Kim, Jun Hwan; Lim, Nam Hun; Yoon, Gil Ho; Han, Ji-Young

    2017-06-01

    Ridge splitting techniques are used for horizontal ridge augmentation in implant dentistry. Recently, a novel engine-driven ridge splitting technique was introduced. This study compared the mechanical forces produced by conventional and engine-driven ridge splitting techniques in porcine mandibles. In 33 pigs, mandibular premolar areas were selected for the ridge splitting procedures, designed as a randomized split-mouth study. The conventional group underwent a chisel-and-mallet procedure (control group, n = 20), and percussive impulse (Newton second, Ns) was measured using a sensor attached to the mallet. In the engine-driven ridge spreader group (test group, n = 23), a load cell was used to measure torque values (Newton centimeter, Ncm). Horizontal acceleration generated during procedures (control group, n = 10 and test group, n = 10) was compared between the groups. After ridge splitting, the alveolar crest width was significantly increased both in the control (1.23 ± 0.45 mm) and test (0.98 ± 0.41 mm) groups with no significant differences between the groups. The average impulse of the control group was 4.74 ± 1.05 Ns. Torque generated by rotation in the test group was 9.07 ± 2.15 Ncm. Horizontal acceleration was significantly less in the test group (0.82 ± 1.05 g) than the control group (64.07 ± 42.62 g) (P < 0.001). Narrow edentulous ridges can be expanded by novel engine-driven ridge spreaders. Within the limits of this study, the results suggested that an engine-driven ridge splitting technique may be less traumatic and less invasive than a conventional ridge splitting technique. © 2016 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  2. Research on Correlations between Academicians' Levels of Organisational Commitment and Their Intention to Quit Their Job: A Comparison of State and Foundation Universities

    ERIC Educational Resources Information Center

    Koc, Mustafa

    2018-01-01

    This study aims to demonstrate the correlations between academicians' organisational commitment and their intention to resign from their job. For this purpose, first the concepts of organisational commitment and quitting the job were considered within the framework of relevant literature, and then hypotheses for the correlations were developed.…

  3. Primary studies of trace quantities of green vegetation in Mono Lake area using 1990 AVIRIS data

    NASA Technical Reports Server (NTRS)

    Chen, Zhi-Kang; Elvidge, Chris D.; Groeneveld, David P.

    1992-01-01

    Our primary results in Jasper Ridge Biological Preserve indicate that high spectral resolution Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) data may provide a substantial advantage in vegetation, based on the chlorophyll red edge feature from 700-780 nm. The chlorophyll red edge was detected for green vegetation cover as low as 4.8 percent. The objective of our studies in Mono Lake area is to continue the experiments performed in Jasper Ridge and to examine the persistence of red edge feature of trace quantities of green vegetation for different plant communities with non-uniform soil backgrounds.

  4. Coastal geology and recent origins for Sand Point, Lake Superior

    USGS Publications Warehouse

    Fisher, Timothy G.; Krantz, David E.; Castaneda, Mario R.; Loope, Walter L.; Jol, Harry M.; Goble, Ronald J.; Higley, Melinda C.; DeWald, Samantha; Hansen, Paul

    2014-01-01

    Sand Point is a small cuspate foreland located along the southeastern shore of Lake Superior within Pictured Rocks National Lakeshore near Munising, Michigan. Park managers’ concerns for the integrity of historic buildings at the northern periphery of the point during the rising lake levels in the mid-1980s greatly elevated the priority of research into the geomorphic history and age of Sand Point. To pursue this priority, we recovered sediment cores from four ponds on Sand Point, assessed subsurface stratigraphy onshore and offshore using geophysical techniques, and interpreted the chronology of events using radiocarbon and luminescence dating. Sand Point formed at the southwest edge of a subaqueous platform whose base is probably constructed of glacial diamicton and outwash. During the post-glacial Nipissing Transgression, the base was mantled with sand derived from erosion of adjacent sandstone cliffs. An aerial photograph time sequence, 1939–present, shows that the periphery of the platform has evolved considerably during historical time, infl uenced by transport of sediment into adjacent South Bay. Shallow seismic refl ections suggest slump blocks along the leading edge of the platform. Light detection and ranging (LiDAR) and shallow seismic refl ections to the northwest of the platform reveal large sand waves within a deep (12 m) channel produced by currents fl owing episodically to the northeast into Lake Superior. Ground-penetrating radar profi les show transport and deposition of sand across the upper surface of the platform. Basal radiocarbon dates from ponds between subaerial beach ridges range in age from 540 to 910 cal yr B.P., suggesting that Sand Point became emergent during the last ~1000 years, upon the separation of Lake Superior from Lakes Huron and Michigan. However, optically stimulated luminescence (OSL) ages from the beach ridges were two to three times as old as the radiocarbon ages, implying that emergence of Sand Point may have begun

  5. Deformation of Forearcs during Aseismic Ridge Subduction

    NASA Astrophysics Data System (ADS)

    Zeumann, S.; Hampel, A.

    2014-12-01

    Subduction of aseismic oceanic ridges causes considerable deformation of the forearc region. To identify the crucial parameters for forearc deformation we created 3D finite-element models representing both erosive and accretive forearcs as well as migrating and non-migrating ridges. As natural examples we choose the Cocos ridge subducting stationary beneath the erosive margin of Costa Rica and the Nazca and Gagua Ridges that migrate along the erosive Peruvian margin and the accretive accretive Ryukyu margin, respectively. A series of models show that the deformation of the forearc depends on the ridge shape (height, width), on the frictional coupling along the plate interface and the mechanical strength of the forearc. The forearc is uplifted and moved sideward during ridge subduction. Strain components show domains of both, shortening and extension. Along the ridge axis, extension occurs except at the ridge tip, where shortening prevails. The strain component normal to the ridge axis reveals extension at the ridge tip and contraction above the ridge flanks. Shortening and extension increase with increasing ridge height. Higher friction coefficients lead to less extension and more shortening. Accretive wedges show larger indentation at the model trench. For stationary ridges (Cocos Ridge) the deformation pattern of the forearc is symmetric with respect to the ridge axis whereas for migrating ridges (Nazca Ridge, Gagua Ridge) the oblique convergence direction leads to asymmetric deformation of the forearc. In case of ridge migration, uplift occurs at the leading flank of the ridge and subsidence at the trailing flank, in agreement with field observations and analogue models. For a model with a 200-km-wide and 1500-m-high ridge (i.e. similar to the dimensions of the Nazca Ridge), the modelled uplift rate at the southern ridge flank of the ridge is ~1 mm/a, which agrees well with uplift rates of ~0.7 mm/a derived from the elevation of marine terraces in southern Peru.

  6. PROPAGATION AND LINKAGE OF OCEANIC RIDGE SEGMENTS.

    USGS Publications Warehouse

    Pollard, David D.; Aydin, Atilla

    1984-01-01

    An investigation was made of spreading ridges and the development of structures that link ridge segments using an analogy between ridges and cracks in elastic plates. The ridge-propagation force and a path factor that controls propagation direction were calculated for echelon ridge segments propagating toward each other. The ridge-propagation force increases as ridge ends approach but then declines sharply as the ends pass, so ridge segments may overlap somewhat. The sign of the path factor changes as ridge ends approach and pass, so the overlapping ridge ends may diverge and then converge following a hook-shaped path. The magnitudes of shear stresses in the plane of the plate and orientations of maximum shear planes between adjacent ridge segments were calculated to study transform faulting. For different loading conditions simulating ridge push, plate pull, and ridge suction, a zone of intense mechanical interaction between adjacent ridge ends in which stresses are concentrated was identified. The magnitudes of mean stresses in the plane of the plate and orientations of principal stress planes were also calculated.

  7. A 9,000-year-old caribou hunting structure beneath Lake Huron.

    PubMed

    O'Shea, John M; Lemke, Ashley K; Sonnenburg, Elizabeth P; Reynolds, Robert G; Abbott, Brian D

    2014-05-13

    Some of the most pivotal questions in human history necessitate the investigation of archaeological sites that are now under water. Nine thousand years ago, the Alpena-Amberley Ridge (AAR) beneath modern Lake Huron was a dry land corridor that connected northeast Michigan to southern Ontario. The newly discovered Drop 45 Drive Lane is the most complex hunting structure found to date beneath the Great Lakes. The site and its associated artifacts provide unprecedented insight into the social and seasonal organization of prehistoric caribou hunting. When combined with environmental and simulation studies, it is suggested that distinctly different seasonal strategies were used by early hunters on the AAR, with autumn hunting being carried out by small groups, and spring hunts being conducted by larger groups of cooperating hunters.

  8. Geomorphology context and characterization of dunefields developed by the southern westerlies at drying Colhué Huapi shallow lake, Patagonia Argentina

    NASA Astrophysics Data System (ADS)

    Montes, Alejandro; Rodríguez, Silvana Soledad; Domínguez, Carlos Eduardo

    2017-10-01

    Patagonia is the only continental territory exposed to the southern westerlies. The speed and frequency of these westerly winds generate a landscape strongly influenced by aeolian processes. This research shows a characterization of depositional and erosive aeolian landforms developed in dunefields associated to Lake Colhué Huapi, in the Extra-Andean Patagonia. Dunefields are located at 45°-46°S and moved in west-east direction due to the southern westerlies. We identified two big groups of active dunefields, one migrating through the dry lakebed of Colhué Huapi and the other migrating eastwards from the lakeshore. The dunefields mainly consist of transverse dunes, barchans, sand shadows and sand sheets. Yardangs, desert pavements, exhumed roots and decapitated soils were recognized in interdune areas. Longitudinal sand ridges, parallel to the prevailing wind direction, often remain preserved after the dunefields have passed. This allows to recognize the path of the dunes in the past. Sand ridges are recognized up to 28 km east from the present coast of the lake and evidenced former dunefields development. We describe the geomorphology context, landforms and sediments supply of dunefields related to the lake dynamics subject to clear tendency to desiccation.

  9. Fine-Branched Ridges

    NASA Image and Video Library

    2015-10-14

    This image from NASA Mars Reconnaissance Orbiter spacecraft shows numerous branching ridges with various degrees of sinuosity. These branching forms resemble tributaries funneling and draining into larger channel trunks towards the upper portion of the scene. The raised relief of these branching ridges suggests that these are ancient channels are inverted due to lithification and cementation of the riverbed sediment, which made it more resistant to erosion than the surrounding material. Wind-blown bedforms are abundant and resemble small ridges that are aligned in an approximately north-south direction. http://photojournal.jpl.nasa.gov/catalog/PIA20006

  10. Fingermark ridge drift.

    PubMed

    De Alcaraz-Fossoul, Josep; Roberts, Katherine A; Feixat, Carme Barrot; Hogrebe, Gregory G; Badia, Manel Gené

    2016-01-01

    Distortions of the fingermark topography are usually considered when comparing latent and exemplar fingerprints. These alterations are characterized as caused by an extrinsic action, which affects entire areas of the deposition and alters the overall flow of a series of contiguous ridges. Here we introduce a novel visual phenomenon that does not follow these principles, named fingermark ridge drift. An experiment was designed that included variables such as type of secretion (eccrine and sebaceous), substrate (glass and polystyrene), and degrees of exposure to natural light (darkness, shade, and direct light) indoors. Fingermarks were sequentially visualized with titanium dioxide powder, photographed and analyzed. The comparison between fresh and aged depositions revealed that under certain environmental conditions an individual ridge could randomly change its original position regardless of its unaltered adjacent ridges. The causes of the drift phenomenon are not well understood. We believe it is exclusively associated with intrinsic natural aging processes of latent fingermarks. This discovery will help explain the detection of certain dissimilarities at the minutiae/ridge level; determine more accurate "hits"; identify potentially erroneous corresponding points; and rethink identification protocols, especially the criteria of "no single minutiae discrepancy" for a positive identification. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

  11. Pequonnock River Basin, Bridgeport, Connecticut. Forest Lake Dam CT 00078. Phase I Inspection Report. National Dam Inspection Program.

    DTIC Science & Technology

    1978-08-01

    Legislation for the protection of wet lands has come too late for this watershed and the remaining small wet lands, if retained, have little value...Ridge Mountains of Central Virginia, 11.55" in Westminister , Maryland and 13" in Steuben County, Pennsylvania. HYDRAULIC ANALYSIS LAKE FOREST Due to

  12. Contextual view of Point Bonita Ridge, showing Bonita Ridge access ...

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

    Contextual view of Point Bonita Ridge, showing Bonita Ridge access road retaining wall and location of Signal Corps Radar (S.C.R.) 296 Station 5 Transmitter Building foundation (see stake at center left), camera facing north - Fort Barry, Signal Corps Radar 296, Station 5, Transmitter Building Foundation, Point Bonita, Marin Headlands, Sausalito, Marin County, CA

  13. Changing characteristics of arctic pressure ridges

    NASA Astrophysics Data System (ADS)

    Wadhams, Peter; Toberg, Nick

    2012-04-01

    The advent of multibeam sonar permits us to obtain full three-dimensional maps of the underside of sea ice. In particular this enables us to distinguish the morphological characteristics of first-year (FY) and multi-year (MY) pressure ridges in a statistically valid way, whereas in the past only a small number of ridges could be mapped laboriously by drilling. In this study pressure ridge distributions from two parts of the Arctic Ocean are compared, in both the cases using mainly data collected by the submarine “Tireless” in March 2007 during two specific grid surveys, in the Beaufort Sea at about 75° N, 140° W (N of Prudhoe Bay), and north of Ellesmere Island at about 83° 20‧ N, 64° W. In the Beaufort Sea the ice was mainly FY, and later melted or broke up as this area became ice-free during the subsequent summer. N of Ellesmere Island the ice was mainly MY. Ridge depth and spacing distributions were derived for each region using the boat's upward looking sonar, combined with distributions of shapes of the ridges encountered, using the Kongsberg EM3002 multibeam sonar. The differing shapes of FY and MY ridges are consistent with two later high-resolution multibeam studies of specific ridges by AUV. FY ridges are found to fit the normal triangular shape template in cross-section (with a range of slope angles averaging 27°) with a relatively constant along-crest depth, and often a structure of small ice blocks can be distinguished. MY ridges, however, are often split into a number of independent solid, smooth blocks of large size, giving an irregular ridge profile which may be seemingly without linearity. Our hypothesis for this difference is that during its long lifetime an MY ridge is subjected to several episodes of crack opening; new cracks in the Arctic pack often run in straight lines across the ridges and undeformed ice alike. Such a crack will open somewhat before refreezing, interpolating a stretch of thin ice into the structure, and breaking up

  14. Variational Ridging in Sea Ice Models

    NASA Astrophysics Data System (ADS)

    Roberts, A.; Hunke, E. C.; Lipscomb, W. H.; Maslowski, W.; Kamal, S.

    2017-12-01

    This work presents the results of a new development to make basin-scale sea ice models aware of the shape, porosity and extent of individual ridges within the pack. We have derived an analytic solution for the Euler-Lagrange equation of individual ridges that accounts for non-conservative forces, and therefore the compressive strength of individual ridges. Because a region of the pack is simply a collection of paths of individual ridges, we are able to solve the Euler-Lagrange equation for a large-scale sea ice field also, and therefore the compressive strength of a region of the pack that explicitly accounts for the macro-porosity of ridged debris. We make a number of assumptions that have simplified the problem, such as treating sea ice as a granular material in ridges, and assuming that bending moments associated with ridging are perturbations around an isostatic state. Regardless of these simplifications, the ridge model is remarkably predictive of macro-porosity and ridge shape, and, because our equations are analytic, they do not require costly computations to solve the Euler-Lagrange equation of ridges on the large scale. The new ridge model is therefore applicable to large-scale sea ice models. We present results from this theoretical development, as well as plans to apply it to the Regional Arctic System Model and a community sea ice code. Most importantly, the new ridging model is particularly useful for pinpointing gaps in our observational record of sea ice ridges, and points to the need for improved measurements of the evolution of porosity of deformed ice in the Arctic and Antarctic. Such knowledge is not only useful for improving models, but also for improving estimates of sea ice volume derived from altimetric measurements of sea ice freeboard.

  15. Distribution, abundance, and resting microhabitat of burbot on Julian's Reef, southwestern Lake Michigan

    USGS Publications Warehouse

    Edsall, Thomas A.; Kennedy, Gregory W.; Horns, William H.

    1993-01-01

    We used a remotely operated submersible vehicle equipped with a color video camera to videotape the lake bed and document the distribution and abundance of burbot Lota lota on a 156-hectare portion of Julian's Reef in southwestern Lake Michigan. The substrates and bathymetry of the study area had been mapped recently by side-scan sonar. Burbot density determined from videotapes covering 6,900 m2 of lake bed at depths of 23-41 m averaged 139 individuals/ hectare (range, 0-571/hectare). This density was substantially higher than the highest burbot density (59-95/hectare) reported in the literature. Burbot were present on the lake bed at depths of 23-36 m, but were most abundant near the crest of the reef at 23-28 m, where the water temperature was 8-13°C, their preferred summer temperature range. Substrates in that temperature range on the reef were bedrock, bedrock ridges, and bedrock and rubble. Burbot were most abundant on the bedrock and rubble. Small fish and macroinvertebrates typically eaten by burbot elsewhere in western Lake Michigan were distributed on the reef according to their summer preferred temperatures and were not seen in abundance where burbot density was highest. We saw no lake trout Salvelinus namaycush on Julian's Reef, although large numbers of juvenile lake trout have been stocked there annually and temperatures on the reef were in the preferred summer temperature range for lake trout.

  16. Distribution, abundance, and resting microhabitat of burbot on Julian's Reef, southwestern Lake Michigan

    USGS Publications Warehouse

    Edsall, Thomas A.; Kennedy, Gregory W.; Horns, William H.

    1993-01-01

    We used a remotely operated submersible vehicle equipped with a color video camera to videotape the lake bed and document the distribution and abundance of burbot Lota lotaon a 156-hectare portion of Julian's Reef in southwestern Lake Michigan. The substrates and bathymetry of the study area had been mapped recently by side-scan sonar. Burbot density determined from videotapes covering 6,900 m2 of lake bed at depths of 23–41 m averaged 139 individuals/ hectare (range, 0–571/hectare). This density was substantially higher than the highest burbot density (59–95/hectare) reported in the literature. Burbot were present on the lake bed at depths of 23–36 m, but were most abundant near the crest of the reef at 23–28 m, where the water temperature was 8–13°C, their preferred summer temperature range. Substrates in that temperature range on the reef were bedrock, bedrock ridges, and bedrock and rubble. Burbot were most abundant on the bedrock and rubble. Small fish and macroinvertebrates typically eaten by burbot elsewhere in western Lake Michigan were distributed on the reef according to their summer preferred temperatures and were not seen in abundance where burbot density was highest. We saw no lake trout Salvelinus namaycush on Julian's Reef, although large numbers of juvenile lake trout have been stocked there annually and temperatures on the reef were in the preferred summer temperature range for lake trout.

  17. Geochemistry of obsidian from Krasnoe Lake on the Chukchi Peninsula (Northeastern Siberia)

    NASA Astrophysics Data System (ADS)

    Popov, V. K.; Grebennikov, A. V.; Kuzmin, Ya. V.; Glascock, M. D.; Nozdrachev, E. A.; Budnitsky, S. Yu.; Vorobey, I. E.

    2017-09-01

    This report considers features of the geochemical composition of obsidian from beach sediments of Krasnoe Lake along the lower course of the Anadyr River, as well as from lava-pyroclastic rocks constituting the lake coastal outcrops and the surrounding branches of Rarytkin Ridge. The two geochemical types of obsidian, for the first time distinguished and researched, correspond in their chemical composition to lavas and ignimbrite-like tuffs of rhyolites from the Rarytkin area. The distinguished types represent the final stage of acidic volcanism in the West Kamchatkan-Koryak volcanic belt. It was assumed that the accumulation of obsidian in coastal pebble beds was caused by the erosion of extrusive domes and pyroclastic flows. The geochemical studies of obsidian artifacts from archeological sites of the regions of the Sea of Okhotsk, the Kolyma River, and the Chukchi Peninsula along with the correlation of geological and archeological samples show that Krasnoe Lake was an important source of "archeological" obsidian in Northeastern Siberia.

  18. The impact of German-speaking academicians on higher education in Turkey.

    PubMed

    Özduman, Koray; Güdük, Mustafa; Elmacı, Ilhan; Pamir, M Necmettin

    2013-01-01

    The transition from the medieval universities to the secular, second generation universities in Turkey occurred in the period from 1773 to 1945. The Ottoman Empire's efforts to establish a higher education system in the eighteenth and nineteenth centuries only aimed at modernization of the armed forces, and the civil effects on the general society were only secondary. After the Turkish Republic was founded in 1923, complete modernization of all institutions of society, including political, social, educational, economic, and law reforms, were initiated by the President Mustafa Kemal Atatürk. His establishment of the modern Istanbul University in Turkey was an experiment unforeseen in the history of education. Step by step, he created a new language, a new alphabet, achieved unified and secular education under government supervision, formed primary and secondary education to support higher education, took expert opinion on forming the new university, and finally established the modern university. German-speaking academicians have played a very important role during the creation of the modern secular university in Turkey. This is a short analysis of this period. Copyright © 2013 Elsevier Inc. All rights reserved.

  19. A 9,000-year-old caribou hunting structure beneath Lake Huron

    PubMed Central

    O’Shea, John M.; Lemke, Ashley K.; Sonnenburg, Elizabeth P.; Reynolds, Robert G.; Abbott, Brian D.

    2014-01-01

    Some of the most pivotal questions in human history necessitate the investigation of archaeological sites that are now under water. Nine thousand years ago, the Alpena-Amberley Ridge (AAR) beneath modern Lake Huron was a dry land corridor that connected northeast Michigan to southern Ontario. The newly discovered Drop 45 Drive Lane is the most complex hunting structure found to date beneath the Great Lakes. The site and its associated artifacts provide unprecedented insight into the social and seasonal organization of prehistoric caribou hunting. When combined with environmental and simulation studies, it is suggested that distinctly different seasonal strategies were used by early hunters on the AAR, with autumn hunting being carried out by small groups, and spring hunts being conducted by larger groups of cooperating hunters. PMID:24778246

  20. Ridge Jumps Associated with Plume-Ridge Interaction 1: Off-axis Heating due to Lithospheric Magma Penetration

    NASA Astrophysics Data System (ADS)

    Mittelstaedt, E.; Ito, G.

    2005-12-01

    In many hot spot-ridge systems, changes in the ridge axis geometry occur between the hot spot centers and nearby mid-ocean ridges in the form of ridge jumps. Such ridge jumps likely occur as a result of anomalous lithospheric stresses associated with mantle plume-lithosphere interaction, as well as weakening of the hot spot lithosphere due to physical and thermal thinning caused by rising buoyant asthenosphere and magma transport through the lithosphere. In this study, we use numerical models to quantify the effects of excess magmatism through the near-ridge lithosphere. Hot spot magmatism can weaken the lithosphere both mechanically through fracturing and thermally through conduction and advection of heat into the plate. Here we focus on the effects of thermal weakening. Using a plane-strain approximation, we examine deformation in a 2-D cross section of a visco-elastic-plastic lithosphere with the finite element code FLAC. The model has isothermal top and bottom boundaries and a prescribed velocity equal to the half spreading rate is imposed on the sides to drive seafloor spreading. The initial condition, as predicted for normal mid-ocean ridges, is a square root of lithospheric age cooling curve with a corner flow velocity field symmetric about the ridge axis. A range of heat inputs are introduced at various plate ages and spreading rates to simulate off-axis magma transport. To reveal the physical conditions that allow for a ridge jump and control its timing, we vary 4 parameters: spreading rate, lithospheric age, crustal thickness and heat input. Results indicate that the heating rate required to produce a ridge jump increases as a function of lithospheric age at the location of magma intrusion. The time necessary for a ridge jump to develop in lithosphere of a particular age decreases with increasing crustal thicknesses. For magma fluxes comparable to those estimated for Galapagos and Iceland, lithospheric heating by the penetrating magma alone is sufficient

  1. 27 CFR 9.182 - Ribbon Ridge.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... Ribbon Ridge. (a) Name. The name of the viticultural area described in this section is “Ribbon Ridge.” (b) Approved Maps. The appropriate maps used to determine the boundaries of the Ribbon Ridge viticultural area... 27 Alcohol, Tobacco Products and Firearms 1 2011-04-01 2011-04-01 false Ribbon Ridge. 9.182...

  2. 27 CFR 9.182 - Ribbon Ridge.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... Ribbon Ridge. (a) Name. The name of the viticultural area described in this section is “Ribbon Ridge.” (b) Approved Maps. The appropriate maps used to determine the boundaries of the Ribbon Ridge viticultural area... 27 Alcohol, Tobacco Products and Firearms 1 2010-04-01 2010-04-01 false Ribbon Ridge. 9.182...

  3. Environmental baseline survey report for West Black Oak Ridge, East Black Oak Ridge, McKinney Ridge, West Pine Ridge and parcel 21D in the vicinity of the East Technology Park, Oak Ridge, Tennessee

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    King, David A.

    2012-11-29

    This environmental baseline survey (EBS) report documents the baseline environmental conditions of five land parcels located near the U.S. Department of Energy?s (DOE?s) East Tennessee Technology Park (ETTP), including West Black Oak Ridge, East Black Oak Ridge, McKinney Ridge, West Pine Ridge, and Parcel 21d. Preparation of this report included the detailed search of federal government records, title documents, aerial photos that may reflect prior uses, and visual inspections of the property and adjacent properties. Interviews with current employees involved in, or familiar with, operations on the real property were also conducted to identify any areas on the property wheremore » hazardous substances and petroleum products, or their derivatives, and acutely hazardous wastes may have been released or disposed. In addition, a search was made of reasonably obtainable federal, state, and local government records of each adjacent facility where there has been a release of any hazardous substance or any petroleum product or their derivatives, including aviation fuel and motor oil, and which is likely to cause or contribute to a release of any hazardous substance or any petroleum product or its derivatives, including aviation fuel or motor oil, on the real property. A radiological survey and soil/sediment sampling was conducted to assess baseline conditions of Parcel 21d that were not addressed by the soils-only no-further-investigation (NFI) reports. Groundwater sampling was also conducted to support a Parcel 21d decision. Based on available data West Black Oak Ridge, East Black Oak Ridge, McKinney Ridge, and West Pine Ridge are not impacted by site operations and are not subject to actions per the Federal Facility Agreement (FFA). This determination is supported by visual inspections, records searches and interviews, groundwater conceptual modeling, approved NFI reports, analytical data, and risk analysis results. Parcel 21d data, however, demonstrate impacts from

  4. Ridges and tidal stress on Io

    USGS Publications Warehouse

    Bart, G.D.; Turtle, E.P.; Jaeger, W.L.; Keszthelyi, L.P.; Greenberg, R.

    2004-01-01

    Sets of ridges of uncertain origin are seen in twenty-nine high-resolution Galileo images, which sample seven locales on Io. These ridges are on the order of a few kilometers in length with a spacing of about a kilometer. Within each locale, the ridges have a consistent orientation, but the orientations vary from place to place. We investigate whether these ridges could be a result of tidal flexing of Io by comparing their orientations with the peak tidal stress orientations at the same locations. We find that ridges grouped near the equator are aligned either north-south or east-west, as are the predicted principal stress orientations there. It is not clear why particular groups run north-south and others east-west. The one set of ridges observed far from the equator (52?? S) has an oblique azimuth, as do the tidal stresses at those latitudes. Therefore, all observed ridges have similar orientations to the tidal stress in their region. This correlation is consistent with the hypothesis that tidal flexing of Io plays an important role in ridge formation. ?? 2004 Elsevier Inc. All rights reserved.

  5. Ridge 2000 Data Management System

    NASA Astrophysics Data System (ADS)

    Goodwillie, A. M.; Carbotte, S. M.; Arko, R. A.; Haxby, W. F.; Ryan, W. B.; Chayes, D. N.; Lehnert, K. A.; Shank, T. M.

    2005-12-01

    Hosted at Lamont by the marine geoscience Data Management group, mgDMS, the NSF-funded Ridge 2000 electronic database, http://www.marine-geo.org/ridge2000/, is a key component of the Ridge 2000 multi-disciplinary program. The database covers each of the three Ridge 2000 Integrated Study Sites: Endeavour Segment, Lau Basin, and 8-11N Segment. It promotes the sharing of information to the broader community, facilitates integration of the suite of information collected at each study site, and enables comparisons between sites. The Ridge 2000 data system provides easy web access to a relational database that is built around a catalogue of cruise metadata. Any web browser can be used to perform a versatile text-based search which returns basic cruise and submersible dive information, sample and data inventories, navigation, and other relevant metadata such as shipboard personnel and links to NSF program awards. In addition, non-proprietary data files, images, and derived products which are hosted locally or in national repositories, as well as science and technical reports, can be freely downloaded. On the Ridge 2000 database page, our Data Link allows users to search the database using a broad range of parameters including data type, cruise ID, chief scientist, geographical location. The first Ridge 2000 field programs sailed in 2004 and, in addition to numerous data sets collected prior to the Ridge 2000 program, the database currently contains information on fifteen Ridge 2000-funded cruises and almost sixty Alvin dives. Track lines can be viewed using a recently- implemented Web Map Service button labelled Map View. The Ridge 2000 database is fully integrated with databases hosted by the mgDMS group for MARGINS and the Antarctic multibeam and seismic reflection data initiatives. Links are provided to partner databases including PetDB, SIOExplorer, and the ODP Janus system. Improved inter-operability with existing and new partner repositories continues to be

  6. Mid-ocean ridge jumps associated with hotspot magmatism

    NASA Astrophysics Data System (ADS)

    Mittelstaedt, Eric; Ito, Garrett; Behn, Mark D.

    2008-02-01

    Hotspot-ridge interaction produces a wide range of phenomena including excess crustal thickness, geochemical anomalies, off-axis volcanic ridges and ridge relocations or jumps. Ridges are recorded to have jumped toward many hotspots including, Iceland, Discovery, Galápagos, Kerguelen and Tristan de Cuhna. The causes of ridge jumps likely involve a number of interacting processes related to hotspots. One such process is reheating of the lithosphere as magma penetrates it to feed near-axis volcanism. We study this effect by using the hybrid, finite-element code, FLAC, to simulate two-dimensional (2-D, cross-section) viscous mantle flow, elasto-plastic deformation of the lithosphere and heat transport in a ridge setting near an off-axis hotspot. Heating due to magma transport through the lithosphere is implemented within a hotspot region of fixed width. To determine the conditions necessary to initiate a ridge jump, we vary four parameters: hotspot magmatic heating rate, spreading rate, seafloor age at the location of the hotspot and ridge migration rate. Our results indicate that the hotspot magmatic heating rate required to initiate a ridge jump increases non-linearly with increasing spreading rate and seafloor age. Models predict that magmatic heating, itself, is most likely to cause jumps at slow spreading rates such as at the Mid-Atlantic Ridge on Iceland. In contrast, despite the higher magma flux at the Galápagos hotspot, magmatic heating alone is probably insufficient to induce a ridge jump at the present-day due to the intermediate ridge spreading rate of the Galápagos Spreading Center. The time required to achieve a ridge jump, for fixed or migrating ridges, is found to be on the order of 10 5-10 6 years. Simulations that incorporate ridge migration predict that after a ridge jump occurs the hotspot and ridge migrate together for time periods that increase with magma flux. Model results also suggest a mechanism for ridge reorganizations not related to

  7. Plio-Pleistocene facies environments from the KBS Member, Koobi Fora Formation: implications for climate controls on the development of lake-margin hominin habitats in the northeast Turkana Basin (northwest Kenya).

    PubMed

    Lepre, Christopher J; Quinn, Rhonda L; Joordens, Josephine C A; Swisher, Carl C; Feibel, Craig S

    2007-11-01

    Climate change is hypothesized as a cause of major events of Plio-Pleistocene East African hominin evolution, but the vertically discontinuous and laterally confined nature of the relevant geological records has led to difficulties with assessing probable links between the two. High-resolution sedimentary sequences from lacustrine settings can provide comprehensive data of environmental changes and detailed correlations with well-established orbital and marine records of climate. Hominin-bearing deposits from Koobi Fora Ridge localities in the northeast Turkana Basin of Kenya are an archive of Plio-Pleistocene lake-margin sedimentation though significant developmental junctures of northern African climates, East African environments, and hominin evolution. This study examines alluvial channel and floodplain, nearshore lacustrine, and offshore lacustrine facies environments for the approximately 136-m-thick KBS Member (Koobi Fora Formation) exposed at the Koobi Fora Ridge. Aspects of the facies environments record information on the changing hydrosedimentary dynamics of the lake margin and give insights into potential climatic controls. Seasonal/yearly climate changes are represented by the varve-like laminations in offshore mudstones and the slickensides, dish-shaped fractures, and other paleosol features overprinted on floodplain strata. Vertical shifts between facies environments, however, are interpreted to indicate lake-level fluctuations deriving from longer-term, dry-wet periods in monsoonal rainfall. Recurrence periods for the inferred lake-level changes range from about 10,000 to 50,000 years, and several are consistent with the average estimated timescales of orbital precession ( approximately 20,000 years) and obliquity ( approximately 40,000 years). KBS Member facies environments from the Koobi Fora Ridge document the development of lake-margin hominin habitats in the northeast Turkana Basin. Environmental changes in these habitats may be a result of

  8. Pesticides and nitrate in groundwater underlying citrus croplands, Lake Wales Ridge, central Florida, 1999-2005.

    USGS Publications Warehouse

    Choquette, Anne F.

    2014-01-01

    This report summarizes pesticide and nitrate (as nitrogen) results from quarterly sampling of 31 surficial-aquifer wells in the Lake Wales Ridge Monitoring Network during April 1999 through January 2005. The wells, located adjacent to citrus orchards and used for monitoring only, were generally screened (sampled) within 5 to 40 feet of the water table. Of the 44 citrus pesticides and pesticide degradates analyzed, 17 were detected in groundwater samples. Parent pesticides and degradates detected in quarterly groundwater samples, ordered by frequency of detection, included norflurazon, demethyl norflurazon, simazine, diuron, bromacil, aldicarb sulfone, aldicarb sulfoxide, deisopropylatrazine (DIA), imidacloprid, metalaxyl, thiazopyr monoacid, oxamyl, and aldicarb. Reconnaissance sampling of five Network wells yielded detection of four additional pesticide degradates (hydroxysimazine, didealkylatrazine, deisopropylhydroxyatrazine, and hydroxyatrazine). The highest median concentration values per well, based on samples collected during the 1999–2005 period (n=14 to 24 samples per well), included 3.05 µg/L (micrograms per liter) (simazine), 3.90 µg/L (diuron), 6.30 µg/L (aldicarb sulfone), 6.85 µg/L (aldicarb sulfoxide), 22.0 µg/L (demethyl norflurazon), 25.0 µg/ (norflurazon), 89 µg/ (bromacil), and 25.5 mg/L (milligrams per liter) (nitrate). Nitrate concentrations exceeded the 10 mg/L (as nitrogen) drinking water standard in one or more groundwater samples from 28 of the wells, and the median nitrate concentration among these wells was 14 mg/L. Sampled groundwater pesticide concentrations exceeded Florida’s health-guidance benchmarks for aldicarb sulfoxide and aldicarb sulfone (4 wells), the sum of aldicarb and its degradates (6 wells), simazine (2 wells), the sum of simazine and DIA (3 wells), diuron (2 wells), bromacil (1 well), and the sum of norflurazon and demethyl norflurazon (1 well). The magnitude of fluctuations in groundwater pesticide

  9. Ridge Regression Signal Processing

    NASA Technical Reports Server (NTRS)

    Kuhl, Mark R.

    1990-01-01

    The introduction of the Global Positioning System (GPS) into the National Airspace System (NAS) necessitates the development of Receiver Autonomous Integrity Monitoring (RAIM) techniques. In order to guarantee a certain level of integrity, a thorough understanding of modern estimation techniques applied to navigational problems is required. The extended Kalman filter (EKF) is derived and analyzed under poor geometry conditions. It was found that the performance of the EKF is difficult to predict, since the EKF is designed for a Gaussian environment. A novel approach is implemented which incorporates ridge regression to explain the behavior of an EKF in the presence of dynamics under poor geometry conditions. The basic principles of ridge regression theory are presented, followed by the derivation of a linearized recursive ridge estimator. Computer simulations are performed to confirm the underlying theory and to provide a comparative analysis of the EKF and the recursive ridge estimator.

  10. Sea ice ridging in the eastern Weddell Sea

    NASA Astrophysics Data System (ADS)

    Lytle, V. I.; Ackley, S. F.

    1991-10-01

    In August 1986, sea ice ridge heights and spatial frequency in the eastern Weddell Sea were measured using a ship-based acoustical sounder. Using a minimum ridge sail height of 0.75 m, a total of 933 ridges were measured along a track length of 415 km. The ridge frequency varied from 0.4 to 10.5 ridges km-1. The mean height of the ridges was found to be about 1.1 m regardless of the ridge frequency. These results are compared to other ridging statistics from the Ross Sea and found to be similar. Comparison with Arctic data, however, indicates that the height and frequency of the ridges are considerably less in the Weddell Sea than in the Arctic. Whereas in the Arctic the mean ridge height tends to increase with the ridge frequency, we found that this was not the case in the Weddell Sea, where the mean ridge height remained constant irrespective of the ridge frequency. Estimates of the contribution of deformed ice to the total ice thickness are generally low except for a single 53-km section where the ridge frequency increased by an order of magnitude. This resulted in an increase in the equivalent mean ice thickness due to ridging from 0.04 m in the less deformed areas to 0.45 m in the highly deformed section. These values were found to be consistent with values obtained from drilled profile lines during the same cruise.

  11. [Comparative study of N, P output and eutrophication risk in runoff water in cross ridge and longitudinal ridge].

    PubMed

    Yu, Xing-Xiu; Ma, Qian; Liu, Qian-Jin; Lü, Guo-An

    2011-02-01

    Field in-situ rainfall simulation tests with two rainfall intensities (40 mm x h(-1) and 70 mm x h(-1)), which were conducted at typical sloping cropland in Yimeng mountainous area, were designed to analyze the output characteristics of dissolved inorganic nitrogen, Inorganic-N (NO3(-)-N, NH4(+) -N) and dissolved phosphorus (DP) in runoff water, as well as to compare the eutrophication risk in this water by calculating three ratios of Inorganic-N/DP, NO3(-) -N/DP, and NH4(+)-N/DP, respectively, in cross ridge and longitudinal ridge tillage methods. Results showed that, under the same rainfall intensity, the DP level in runoff water was higher in cross ridge than longitudinal ridge, while the change of different Inorganic-N level between the two tillage methods were not consistent. Cross ridge could effectively reduce runoff and the output rate of Inorganic-N and DP when compared to the longitudinal ridge tillage, which would be more outstanding with the increases of rainfall intensities. The losses of Inorganic-N and DP in runoff water were 43% and 5% less, respectively, in cross ridge than longitudinal ridge at the 40 mm x h(-1) rainfall intensity, and were 68% and 55%, respectively, at 70 mm x h(-1). The higher Inorganic-N/DP and NO3(-) -N/DP ratios suggest that runoff water from either cross ridge or longitudinal ridge tillage have a certain eutrophication risk, which present an increasing trend during the precipitation-runoff process. Compared with longitudinal ridge, cross ridge can not only hinder the increasing trend of eutrophication risk, but also can significantly lower it, and thus effectively reduce the effect of sloping cropland runoff on the eutrophication processes of receiving waters.

  12. Comparison of buried sand ridges and regressive sand ridges on the outer shelf of the East China Sea

    NASA Astrophysics Data System (ADS)

    Wu, Ziyin; Jin, Xianglong; Zhou, Jieqiong; Zhao, Dineng; Shang, Jihong; Li, Shoujun; Cao, Zhenyi; Liang, Yuyang

    2017-06-01

    Based on multi-beam echo soundings and high-resolution single-channel seismic profiles, linear sand ridges in U14 and U2 on the East China Sea (ECS) shelf are identified and compared in detail. Linear sand ridges in U14 are buried sand ridges, which are 90 m below the seafloor. It is presumed that these buried sand ridges belong to the transgressive systems tract (TST) formed 320-200 ka ago and that their top interface is the maximal flooding surface (MFS). Linear sand ridges in U2 are regressive sand ridges. It is presumed that these buried sand ridges belong to the TST of the last glacial maximum (LGM) and that their top interface is the MFS of the LGM. Four sub-stage sand ridges of U2 are discerned from the high-resolution single-channel seismic profile and four strikes of regressive sand ridges are distinguished from the submarine topographic map based on the multi-beam echo soundings. These multi-stage and multi-strike linear sand ridges are the response of, and evidence for, the evolution of submarine topography with respect to sea-level fluctuations since the LGM. Although the difference in the age of formation between U14 and U2 is 200 ka and their sequences are 90 m apart, the general strikes of the sand ridges are similar. This indicates that the basic configuration of tidal waves on the ECS shelf has been stable for the last 200 ka. A basic evolutionary model of the strata of the ECS shelf is proposed, in which sea-level change is the controlling factor. During the sea-level change of about 100 ka, five to six strata are developed and the sand ridges develop in the TST. A similar story of the evolution of paleo-topography on the ECS shelf has been repeated during the last 300 ka.

  13. Lignin phenols in sediments of Lake Baikal, Siberia: Application to paleoenvironmental studies

    USGS Publications Warehouse

    Orem, W.H.; Colman, Steven M.; Lerch, H.E.

    1997-01-01

    Sediments from three cores obtained from distinct depositional environments in Lake Baikal, Siberia were analyzed for organic carbon, total nitrogen and lignin phenol concentration and composition. Results were used to examine changes in paleoenvironmental conditions during climatic cycles of the late Quaternary (< 125 ka). Average organic carbon, and total nitrogen concentrations, atomic C/N ratios and organic carbon accumulation rates were significantly higher in the Holocene compared with the late Pleistocene, reflecting overall warmer temperatures and increased runoff during the Holocene. A Holocene maximum in organic carbon was observed at about 6 ka, and may represent the warmest wettest period of the Holocene. At one site (Academician Ridge) pronounced late Pleistocene maxima in organic carbon and biogenic silica were observed at about 80-85 ka, probably indicative of an interstadial period with enhanced aquatic productivity. Total sedimentary lignin phenol contents were generally lower in the late Pleistocene compared to the Holocene, but with several peaks in concentration during the late Pleistocene. These late Pleistocene peaks in total sedimentary lignin content (dated at about 80, 50 and 30 ka) directly precede or occur during peaks in sedimentary biogenic silica contents. These periods likely represent relatively warm interstadial times, with increased precipitation producing the observed increase in terrestrial runoff and aquatic productivity. Lignin phenol ratios (S/V, C/V and P/V) were used to examine changes in terrestrial vegetation type resulting from changes in paleoenvironmental conditions during the late Pleistocene. A degree of caution must be used in the interpretation of these ratios with regard to vegetation sources and paleoenvironmental conditions, because of potential compositional changes in lignin resulting from biodegradation. Nevertheless, results show that long glacial periods were characterized by terrestrial vegetation composed

  14. Researching Together: A CTSA Partnership of Academicians and Communities for Translation

    PubMed Central

    Nearing, Kathryn; Felzien, Maret; Green, Larry; Calonge, Ned; Pineda‐Reyes, Fernando; Jones, Grant; Tamez, Montelle; Miller, Sara; Kramer, Andrew

    2013-01-01

    Abstract Background The Colorado Clinical and Translational Sciences Institute (CCTSI) aims to translate discovery into clinical practice. The Partnership of Academicians and Communities for Translation (PACT) represents a robust campus–community partnership. Methods The CCTSI collected data on all PACT activities including meeting notes, staff activity logs, stakeholder surveys and interviews, and several key component in‐depth evaluations. Data analysis by Evaluation and Community Engagement Core and PACT Council members identified critical shifts that changed the trajectory of community engagement efforts. Results Ten “critical shifts” in six broad rubrics created change in the PACT. Critical shifts were decision points in the development of the PACT that represented quantitative and qualitative changes in the work and trajectory. Critical shifts occurred in PACT management and leadership, financial control and resource allocation, and membership and voice. Discussion The development of a campus–community partnership is not a smooth linear path. Incremental changes lead to major decision points that represent an opportunity for critical shifts in developmental trajectory. We provide an enlightening, yet cautionary, tale to others considering a campus–community partnership so they may prepare for crucial decisions and critical shifts. The PACT serves as a genuine foundational platform for dynamic research efforts aimed at eliminating health disparities. PMID:24127922

  15. Depositional history and neotectonics in Great Salt Lake, Utah, from high-resolution seismic stratigraphy

    USGS Publications Warehouse

    Colman, Steven M.; Kelts, K.R.; Dinter, D.A.

    2002-01-01

    High-resolution seismic-reflection data from Great Salt Lake show that the basinal sediment sequence is cut by numerous faults with N-S and NE-SW orientations. This faulting shows evidence of varied timing and relative offsets, but includes at least three events totaling about 12 m following the Bonneville phase of the lake (since about 13.5 ka). Several faults displace the uppermost sediments and the lake floor. Bioherm structures are present above some faults, which suggests that the faults served as conduits for sublacustrine discharge of fresh water. A shallow, fault-controlled ridge between Carrington Island and Promontory Point, underlain by a well-cemented pavement, separates the main lake into two basins. The pavement appears to be early Holocene in age and younger sediments lap onto it. Onlap-offlap relationships, reflection truncations, and morphology of the lake floor indicate a low lake, well below the present level, during the early Holocene, during which most of the basin was probably a playa. This low stand is represented by irregular reflections in seismic profiles from the deepest part of the basin. Other prominent reflectors in the profiles are correlated with lithologic changes in sediment cores related to the end of the Bonneville stage of the lake, a thick mirabilite layer in the northern basin, and the Mazama tephra. Reflections below those penetrated by sediment cores document earlier lacustrine cycles. ?? 2002 Elsevier Science B.V. All rights reserved.

  16. Tracing historical trends of Hg in the Mississippi River using Hg concentrations and Hg isotopic compositions in a lake sediment core, Lake Whittington, Mississippi, USA

    USGS Publications Warehouse

    Gray, John E.; Van Metre, Peter C.; Pribil, Michael J.; Horowitz, Arthur J.

    2015-01-01

    Concentrations and isotopic compositions of mercury (Hg) in a sediment core collected from Lake Whittington, an oxbow lake on the Lower Mississippi River, were used to evaluate historical sources of Hg in the Mississippi River basin. Sediment Hg concentrations in the Lake Whittington core have a large 10-15 y peak centered on the 1960s, with a maximum enrichment factor relative to Hg in the core of 4.8 in 1966. The Hg concentration profile indicates a different Hg source history than seen in most historical reconstructions of Hg loading. The timing of the peak is consistent with large releases of Hg from Oak Ridge National Laboratory (ORNL), primarily in the late 1950s and 1960s. Mercury was used in a lithiumisotope separation process by ORNL and an estimated 128Mg (megagrams) of Hgwas discharged to a local stream that flows into the Tennessee River and, eventually, the Mississippi River. Mass balance analyses of Hg concentrations and isotopic compositions in the Lake Whittington core fit a binary mixing model with a Hg-rich upstream source contributing about 70% of the Hg to Lake Whittington at the height of the Hg peak in 1966. This upstream Hg source is isotopically similar to Hg isotope compositions of stream sediment collected downstream near ORNL. It is estimated that about one-half of the Hg released from the ORNL potentially reached the LowerMississippi River basin in the 1960s, suggesting considerable downstream transport of Hg. It is also possible that upstream urban and industrial sources contributed some proportion of Hg to Lake Whittington in the 1960s and 1970s.

  17. Ice-Ridge Pile Up and the Genesis of Martian "Shorelines"

    NASA Technical Reports Server (NTRS)

    Barnhart, C. J.; Tulaczyk, S.; Asphaug, E.; Kraal, E. R.; Moore, J.

    2005-01-01

    Unique geomorphologic features such as basin terraces exhibiting topographic continuity have been found within several Martian craters as shown in Viking, MOC, and THEMIS images. These features, showing similarity to terrestrial shorelines, have been mapped and cataloged with significant effort [1]. Currently, open wave action on the surface of paleolakes has been hypothesized as the geomorphologic agent responsible for the generation of these features [2]. As consequence, feature interpretations, including shorelines, wave-cut benches, and bars are, befittingly, lacustrine. Because such interpretations and their formation mechanisms have profound implications for the climate and potential biological history of Mars, confidence is crucial. The insight acquired through linked quantitative modeling of geomorphologic agents and processes is key to accurately interpreting these features. In this vein, recent studies [3,4] involving the water wave energy in theoretical open water basins on Mars show minimal erosional effects due to water waves under Martian conditions. Consequently, sub-glacial lake flattens the surface, produces a local velocity increase over the lake, and creates a deviation of the ice flow from the main flow direction [11]. These consequences of ice flow are observed at Lake Vostok, Antarctica an excellent Martian analogue [11]. Martian observations include reticulate terrain exhibiting sharp inter-connected ridges speculated to reflect the deposition and reworking of ice blocks at the periphery of ice-covered lakes throughout Hellas [12]. Our model determines to what extent ice, a terrestrial geomorphologic agent, can alter the Martian landscape. Method: We study the evolution of crater ice plugs as the formation mechanism of surface features frequently identified as shorelines. In particular, we perform model integrations involving parameters such as ice slope and purity, atmospheric pressure and temperature, crater shape and composition, and an

  18. Wrinkle ridges of Arcadia Planitia, Mars

    NASA Technical Reports Server (NTRS)

    Plescia, J. B.

    1993-01-01

    Wrinkle ridges of Arcadia Planitia were examined to determine their morphology, spatial distribution, and the amount of crustal shortening and strain they accommodate. Ridges trend generally northward, but their orientation and distribution are strongly controlled by the relief of the underlying hobby material. Ridges begin or end at inselbergs of older terrain and are associated with buried craters. Arcadia Planitia ridges have an average width of 3425 m and accommodate an average folding shortening of 3 m and a faulting shortening of 55 m; mean total shortening is 57 m. Three east-west transects were constructed at 20 deg 25 deg and 28 deg N to estimate regional shortening and strain. Average total shortening across the transects is about 900 m, corresponding to a regional compressive strain of 0.06 percent. The total shortening and compression across Arcadia Planitia are less than in Lungae Planum. Faults associated with the Arcadia ridges are inferred to have a westward dip compared with an eastward dip for Lungae Planum ridges. The general levels of compression and symmetric orientation of the ridges suggest a regionally organized stress system.

  19. Implications of the miocene(?) crooked ridge river of northern arizona for the evolution of the colorado river and grand canyon

    USGS Publications Warehouse

    Lucchitta, Ivo; Holm, Richard F.; Lucchitta, Baerbel K.

    2013-01-01

    The southwesterly course of the probably pre–early Miocene and possibly Oligocene Crooked Ridge River can be traced continuously for 48 km and discontinuously for 91 km in northern Arizona (United States). The course is visible today in inverted relief. Pebbles in the river gravel came from at least as far northeast as the San Juan Mountains (Colorado). The river valley was carved out of easily eroded Jurassic and Cretaceous rocks whose debris overloaded the river with abundant detritus, probably steepening the gradient. After the river became inactive, the regional drainage network was rearranged three times, and the nearby Four Corners region was lowered 1–2 km by erosion. The river provides constraints on the early evolution of the Colorado River and Grand Canyon. Continuation of this river into lakes in Arizona or Utah is unlikely, as is integration through Grand Canyon by lake spillover. The downstream course of the river probably was across the Kaibab arch in a valley roughly coincident with the present eastern Grand Canyon. Beyond this point, the course may have continued to the drainage basin of the Sacramento River, or to the proto–Snake River drainage. Crooked Ridge River was beheaded by the developing San Juan River, which pirated its waters and probably was tributary to a proto–Colorado River, flowing roughly along its present course west of the Monument upwarp.

  20. Trace elements in ocean ridge basalts

    NASA Technical Reports Server (NTRS)

    Kay, R. W.; Hubbard, N. J.

    1978-01-01

    A study is made of the trace elements found in ocean ridge basalts. General assumptions regarding melting behavior, trace element fractionation, and alteration effects are presented. Data on the trace elements are grouped according to refractory lithophile elements, refractory siderophile elements, and volatile metals. Variations in ocean ridge basalt chemistry are noted both for regional and temporal characteristics. Ocean ridge basalts are compared to other terrestrial basalts, such as those having La/Yb ratios greater than those of chondrites, and those having La/Yb ratios less than those of chondrites. It is found that (1) as compared to solar or chondrite ratios, ocean ridge basalts have low ratios of large, highly-charged elements to smaller less highly-charged elements, (2) ocean ridge basalts exhibit low ratios of volatile to nonvolatile elements, and (3) the transition metals Cr through Zn in ocean ridge basalts are not fractionated more than a factor of 2 or 3 from the chondritic abundance ratios.

  1. Global survey of lunar wrinkle ridge formation times

    NASA Astrophysics Data System (ADS)

    Yue, Z.; Michael, G. G.; Di, K.; Liu, J.

    2017-11-01

    Wrinkle ridges are a common feature of the lunar maria and record subsequent contraction of mare infill. Constraining the timing of wrinkle ridge formation from crater counts is challenging because they have limited areal extent and it is difficult to determine whether superposed craters post-date ridge formation or have alternatively been uplifted by the deformation. Some wrinkle ridges do allow determination to be made. This is possible where a ridge shows a sufficiently steep boundary or scarp that can be identified as deforming an intersecting crater or the crater obliterates the relief of the ridge. Such boundaries constitute only a small fraction of lunar wrinkle ridge structures yet they are sufficiently numerous to enable us to obtain statistically significant crater counts over systems of structurally related wrinkle ridges. We carried out a global mapping of mare wrinkle ridges, identifying appropriate boundaries for crater identification, and mapping superposed craters. Selected groups of ridges were analyzed using the buffered crater counting method. We found that, except for the ridges in mare Tranquilitatis, the ridge groups formed with average ages between 3.5 and 3.1 Ga ago, or 100-650 Ma after the oldest observable erupted basalts where they are located. We interpret these results to suggest that local stresses from loading by basalt fill are the principal agent responsible for the formation of lunar wrinkle ridges, as others have proposed. We find a markedly longer interval before wrinkle ridge formation in Tranquilitatis which likely indicates a different mechanism of stress accumulation at this site.

  2. Formation of ferric iron crusts in Quaternary sediments of Lake Baikal, Russia, and implications for paleoclimate

    USGS Publications Warehouse

    Deike, R.G.; Granina, L.; Callender, E.; McGee, J.J.

    1997-01-01

    Phosphate-bearing, ferric iron and siliceous crusts ranging in age from Recent to approximately 65,000 yr B.P. are observed in sediments of Lake Baikal. In younger sediments the crusts are at the base of a spectrum of secondary iron and manganese oxides that accumulate near the sediment/water interface in the zone of positive oxidation potential beneath an oxygenated water column. In areas where the average Quaternary sedimentation rates have been slow (e.g. 0.026 mm/yr), the crusts are more common, and span a wider range of ages. No crusts have been found where the Quaternary sedimentation mode has been deltaic and rapid (0.15 mm/yr). Independent core correlation based on magnetic properties of the sediment suggests that crusts can be correlated over most of Academician Ridge, an area that is particularly sensitive to climatic events affecting the concentration of suspended sediment. These crusts may be indicative of periods of low suspended sediment concentration, which occur during sustained transitions from glacial periods of high detrital input, to interglacial periods of high diatom sedimentation. The crusts are dominated by iron-rich and siliceous amorphous mineral phases, with an FeO:SiO2 by weight of 3:1. Regardless of age or location in the lake the Fe phase always includes Ca, P and Mn. Extensive microprobe data for these four elements recast as normalized elemental weight percent reveal linear trends of Ca:P and Fe:P. With increasing P, Ca also increases such that the two elements maintain a linear relationship passing very close to the origin and with a mean molar Ca:P=0.3 (too low for well-characterized apatite). Conversely, with increasing P, Fe decreases (mean molar Fe:P=3.4). There is no correlation between Mn and P. Molar Fe:P ratios for vivianite (an Fe(II) phosphate mineral observed in sediments closely below some crusts) are clustered around a stoichiometric composition. The covariant increase in Ca:P and the corresponding decrease in Fe:P may

  3. Ridge interaction features of the Line Islands

    NASA Astrophysics Data System (ADS)

    Konter, J. G.; Koppers, A. A. P.; Storm, L. P.

    2016-12-01

    The sections of Pacific absolute plate motion history that precede the Hawaii-Emperor and Louisville chains are based on three chains: the Line Islands-Mid-Pacific Mountains, the Hess Rise-Shatsky Rise, and the Marshall Islands-Wake Islands (Rurutu hotspot). Although it has been clear that the Line Islands do not define a simple age progression (e.g. Schlanger et al., 1984), the apparent similarity to the Emperor Seamount geographic trend has been used to extend the overall Hawaii-Emperor track further into the past. However, we show here that plate tectonic reconstructions suggest that the Mid-Pacific Mountains (MPMs) and Line Islands (LIs) were erupted near a mid-ocean ridge, and thus these structures do not reflect absolute plate motion. Moverover, the morphology and geochemistry of the volcanoes show similarities with Pukapuka Ridge (e.g. Davis et al., 2002) and the Rano Rahi seamounts, presumed to have a shallow origin. Modern 40Ar/39Ar ages show that the LIs erupted at various times along the entire volcanic chain. The oldest structures formed within 10 Ma of plate formation. Given the short distance to the ridge system, large aseismic volcanic ridges, such as Necker Ridge and Horizon Guyot may simply reflect a connection between MPMs and the ridge, similar to the Pukapuka Ridge. The Line Islands to the south (including Karin Ridge) define short subchains of elongated seamounts that are widespread, resembling the Rano Rahi seamount field. During this time, the plate moved nearly parallel to the ridge system. The change from few large ridges to many subchains may reflect a change in absolute plate motion, similar to the Rano Rahi field. Here, significant MPMs volcanism is no longer connected to the ridge along plate motion. Similar to Pukapuka vs. Rano Rahi, the difference in direction between plate motion and the closest ridge determines whether larger ridges or smaller seamount subchains are formed. The difference between the largest structures (MPMs and LIs

  4. Surface radiological investigations at White Wing Scrap Yard, Oak Ridge Reservation, Oak Ridge, Tennessee

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Williams, J.K.; Rodriguez, R.E.; Uziel, M.S.

    1991-09-01

    A surface radiological scoping survey of accessible areas at the White Wing Scrap Yard (Waste Area Grouping 11 (WAG 11)) was conducted intermittently from December 1989 through July 1991 by members of the Measurement Applications and Development Group, Health and Safety Research Division, Oak Ridge National Laboratory (ORNL) at the request of Environmental Restoration Program personnel at ORNL. The White Wing Scrap Yard is an estimated 30-acre, predominately wooded area located on the western edge of East Fork Ridge in the McNew Hollow area on the US Department of Energy's Oak Ridge Reservation. The scrap yard was formerly used formore » aboveground storage of contaminated material (e.g., steel tanks, metal, glass, concrete, and miscellaneous industrial trash) from the Oak Ridge K-25 Site, Oak Ridge Y-12 Plant, and ORNL. The purposes of this cursory investigation were (1) to provide an updated contamination status of the site by locating and interpreting the presence, nature, and extent of surface radiological contamination and (2) to provide a basis for the formulation of interim corrective action to limit human exposures to radioactivity and minimize the potential for contaminant dispersion. 13 refs., 17 figs., 5 tabs.« less

  5. Periodontal considerations for esthetics: edentulous ridge augmentation.

    PubMed

    Rosenberg, E S; Cutler, S A

    1993-01-01

    Edentulous ridge augmentation is a plastic surgical technique that is performed to improve patient esthetics when unsightly, deformed ridges exist. This article describes the etiology of ridge deformities and the many procedures that can be executed to achieve an esthetic, functional result. Historically, soft-tissue mucogingival techniques were described to augment collapsed ridges. Pedicle grafts, free soft-tissue grafts, and subepithelial connective tissue grafts are predictable forms of therapy. More recently, ridge augmentation techniques were developed that regenerate the lost periodontium. These include allografts, bioglasses, guided tissue regenerative procedures, and tissue expansion.

  6. Hydrogeologic setting, water budget, and preliminary analysis of ground-water exchange at Lake Starr, a seepage lake in Polk County, Florida

    USGS Publications Warehouse

    Swancar, Amy; Lee, T.M.; O'Hare, T. M.

    2000-01-01

    Lake Starr, a 134-acre seepage lake of multiple-sinkhole origin on the Lake Wales Ridge of central Florida, was the subject of a detailed water-budget study from August 1996 through July 1998. The study monitored the effects of hydrogeologic setting, climate, and ground-water pumping on the water budget and lake stage. The hydrogeologic setting of the Lake Starr basin differs markedly on the two sides of the lake. Ground water from the surficial aquifer system flows into the lake from the northwest side of the basin, and lake water leaks out to the surficial aquifer system on the southeast side of the basin. Lake Starr and the surrounding surficial aquifer system recharge the underlying Upper Floridan aquifer. The rate of recharge to the Upper Floridan aquifer is determined by the integrity of the intermediate confining unit and by the downward head gradient between the two aquifers. On the inflow side of the lake, the intermediate confining unit is more continuous, allowing ground water from the surficial aquifer system to flow laterally into the lake. Beneath the lake and on the southeast side of the basin, breaches in the intermediate confining unit enhance downward flow to the Upper Floridan aquifer, so that water flows both downward and laterally away from the lake through the ground-water flow system in these areas. An accurate water budget, including evaporation measured by the energy-budget method, was used to calculate net ground-water flow to the lake, and to do a preliminary analysis of the relation of net ground-water fluxes to other variables. Water budgets constructed over different timeframes provided insight on processes that affect ground-water interactions with Lake Starr. Weekly estimates of net ground-water flow provided evidence for the occurrence of transient inflows from the nearshore basin, as well as the short-term effects of head in the Upper Floridan aquifer on ground-water exchange with the lake. Monthly water budgets showed the effects

  7. Effects on Ridge Segmentation, Magmatic Plumbing and Eruption Style Caused by Weak Hot-spot to Ridge Interaction: the Central Indian Ridge and Rodrigues Hot-spot Couplet.

    NASA Astrophysics Data System (ADS)

    Murton, B. J.; Parson, L. M.; Sauter, D.

    2001-12-01

    The intermediate spreading, Central Indian Ridge (CIR) forms a couplet with a weak hot-spot of which the Rodrigues archipelago is an expression. Recently collected bathymetry shows that despite having little in the way of a significant topographic swell, the hot-spot is associated with a change in offset sense across adjacent transforms of the CIR causing the ridge to draw nearer to the Rodrigues island system. The most proximal ridge segment of the CIR is over 20km long and comprises three non-transform bounded sub-segments. The most northerly sub-segment has a shallow (<3000m), narrow (<5km) and featureless flat rift valley. TOBI sidescan sonar imagery shows that the segment is host to a 15km-long, 5km-wide single sheet flow. Elsewhere in the segment the valley floor is characterised by long (>5km), narrow (<1km) ridges that often terminate in conical seamounts. These ridges are the loci of some of the acoustically freshest volcanic facies in the rift valley. Samples recovered from these ridges have similar petrology along strike. With increasing distance south along the CIR, the ridge segments are typically 500m deeper than to the north. Here they are about 75km long and bounded by transform offsets that are 50 km long. However, even in the deepest parts of these segments, where the axial floor is over 4000m deep at the ridge-transform-intersections, there is fresh lava and other evidence for abundant volcanic activity. Within these segments, the rift valley comprises mainly seamounts and hummocky volcanic features. We believe the westward stepping trend of the CIR towards the Rodrigues islands is a function of the hot spot. The elevated temperature and volatile content to the west reduces mantle viscosity which, combined with thinner and hence weaker lithosphere, influencec the loci of initial oceanic rifting and the relative position of the ridge axis. The unusually great length of the northern segment has a similar origin with the presence of thin and weak

  8. Carslberg Ridge and Mid-Atlantic Ridge: Slow-spreading Apparent Analogs

    NASA Astrophysics Data System (ADS)

    Rona, P. A.; Murton, B. J.; Bostrom, K.; Widenfalk, L.; Melson, W. G.; O'Hearn, T.; Cronan, D. S.; Jenkins, W. J.

    2005-12-01

    We compare morphology, tectonics, petrology, and hydrothermal activity of a known section of the Mid-Atlantic Ridge (MAR) between the Kane and Atlantis fracture zones (full multi-beam coverage 21N to 31N) to the lesser known Carlsberg Ridge (CR; limited multi-beam coverage plus satellite altimetry). The CR extends from the Owen Fracture Zone (10N) to the Vityaz Fracture Zone (5S) and spreads at half-rates (~1.2-1.8 cm/yr) similar to the MAR: 1) Morphology: Both ridges exhibit distinct segmentation (primarily sinistral) and axial valleys with high floor to crest relief (range 1122-1771 m). Average lengths of segments (CR: 70 km; MAR: 50 km) and crest-to crest width of the axial valley are greater on the CR (40 km) than MAR (23 km). Axial volcanic ridges form the neovolcanic zone on both ridges, typically 2.6 km wide and 213 m high on the CR. Average water depth near segment centers is greater on the MAR (3933 m) than the CR (3564 m). V-shaped patterns oblique to the spreading axis are present on both ridges. 2) Tectonics: Segments on each ridge are predominantly separated by short-offset (<30 km) non-transform discontinuities with longer transform faults generally spaced hundreds of kilometers apart. Bulls-eye Mantle Bouguer Lows (-30 to -50 mgal) are present at centers of spreading segments on both ridges. Metamorphic core complexes of lower crust and upper mantle are present on the MAR section (at fracture zones) and at least at one locality at 58.33E on the CR. 3) Petrology: MORB composition from our 20 stations along the CR fall into the MORB family, with no evidence of hotspot inputs (no excess K or Nb), or extreme fractionation, similar to the MAR section. REE and trace element patterns between 57E and 61E on the CR indicate increasing melt depletion to the northwest, while glasses exhibit a striking systematic increase in MgO (decrease in fractionation) to the northwest and attain among the most primitive composition of any ocean ridge adjacent to the Owen

  9. Evolution of salt and hydrocarbon migration: Sweet Lake area, Cameron Parish, Louisiana

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Spencer, J.A.; Sharpe, C.L.

    The interpretation of seismic, gravity, and well data in northern Cameron Parish, Louisiana suggest that lateral salt flow has influenced the area`s structural evolution, depositional patterns, and hydrocarbon migration. Sweet Lake Field has produced over 46 MMBO and 15 BCFG from Middle Miocene deltaic sands. The structural closure is a downthrown anticline on a fault controlled by the underlying salt feature. Sweet Lake Field overlies an allochthonous salt mass that was probably once part of an ancestral salt ridge extending from Hackberry to Big Lake fields. Nine wells encountering top of salt and several seismic lines define a detached saltmore » feature underlying over twenty square miles at depths from 8500-18,000 ft. Salt withdrawal in the East Hackberry-Big Lake area influenced the depositional patterns of the Oligocene lower Hackberry channel systems. Progradation of thick Middle Oligocene Camerina (A) and Miogypsinoides sands into the area caused salt thinning and withdrawal resulting in the development and orientation of the large Marginulina-Miogypsinoides growth fault northwest of Sweet Lake. Additional evidence for the southeast trend of the salt is a well approximately two miles southeast of Sweet Lake which encountered salt at approximately 19,800 ft. High quality 2-D and 3-D seismic data will continue to enhance the regional understanding of the evolving salt structures in the onshore Gulf Coast and the local understanding of hydrocarbon migration. Additional examples of lateral salt flow will be recognized and some may prove to have subsalt hydrocarbon potential.« less

  10. Ridge jumps associated with plume-ridge interaction: Mantle plume-lithosphere interaction and hotspot magmatism

    NASA Astrophysics Data System (ADS)

    Mittelstaedt, E.; Ito, G.

    2007-12-01

    Interaction of mantle plumes and young lithosphere near mid-ocean ridges can lead to changes in spreading geometry by shifts of the ridge-axis toward the plume as seen at various hotspots, notably Iceland and the Galapagos. Previous work has shown that, with a sufficient magma flux, heating of the lithosphere by magmatism can significantly weaken the plate and, in some cases, could cause ridge jumps. Upwelling hot asthenosphere can also weaken the plate through thermal and mechanical thinning of the lithosphere. Using the finite element code CITCOM, we solve the equations of continuity, momentum and energy to examine deformation in near-ridge lithosphere associated with relatively hot upwelling asthenosphere and seafloor spreading. The mantle and lithosphere obey a non-Newtonian viscous rheology with plastic failure in the cold part of the lithosphere simulated by imposing an effective yield stress. Temperatures of the lithospheric thermal boundary region are initially given a square-root of age thermal profile while a hot patch is placed at the bottom to initiate a mantle-plume like upwelling. The effect of upwelling asthenosphere on ridge jumps is evaluated by varying three parameters: the plume excess temperature, the spreading rate and the distance of the plume from the ridge axis. Preliminary results show plume related thinning and weakening of the lithosphere over a wide area (100's of km's) with the rate of thinning increasing with the excess temperature of the plume. Initially, thinning occurs as the plume approaches the lithosphere and asthenospheric material is forced out of the way. As the plume material comes into contact with the lithosphere, thinning occurs through heating and mechanical removal of the thermal boundary layer. Thinning of the lithosphere is one of the primary factors in achieving a ridge jump. Another is large tensile stresses which can facilitate the initiation of rifting at this weakened location. Model stresses induced by the

  11. Ponding, draining and tilting of the Cerberus Plains; a cryolacustrine origin for the sinuous ridge and channel networks in Rahway Vallis, Mars

    NASA Astrophysics Data System (ADS)

    Ramsdale, J. D.; Balme, M. R.; Conway, S. J.; Gallagher, C.

    2015-06-01

    filling by fluvial flooding, followed by lake drainage. Drainage could have occurred as a consequence of an ice or debris-dam failure within (or during the formation of) the large, nearby fluvial flood channel Marte Vallis. If the lake was partly or largely frozen prior to drainage, this offers a possible explanation for the sinuous ridge systems. Hence, although the sinuous ridges provide some of the most compelling morphological analogues of terrestrial eskers yet observed, we conclude that the contextual evidence for this interpretation in Rahway Vallis is not strong, and instead they are better explained in the context of a frozen or partially frozen lake or cryolacustrine model.

  12. Large-scale deformation associated with ridge subduction

    USGS Publications Warehouse

    Geist, E.L.; Fisher, M.A.; Scholl, D. W.

    1993-01-01

    Continuum models are used to investigate the large-scale deformation associated with the subduction of aseismic ridges. Formulated in the horizontal plane using thin viscous sheet theory, these models measure the horizontal transmission of stress through the arc lithosphere accompanying ridge subduction. Modelling was used to compare the Tonga arc and Louisville ridge collision with the New Hebrides arc and d'Entrecasteaux ridge collision, which have disparate arc-ridge intersection speeds but otherwise similar characteristics. Models of both systems indicate that diffuse deformation (low values of the effective stress-strain exponent n) are required to explain the observed deformation. -from Authors

  13. Volcanoclastics of the Walvis Ridge

    NASA Astrophysics Data System (ADS)

    Eroshenko, D. V.; Kharin, G. S.

    2018-03-01

    The paper generalizes the distribution of volcanoclastic material in the Cenozoic sedimentary cover of the Walvis Ridge, made on the basis of the DSDP (Deep Sea Drilling Projects) and ODP (Ocean Drilling Program). The cycles of volcanoclastic accumulation have been distinguished. It has been proved that the distribution of the material in the Paleogene primary reflects the dynamics of volcanism of the ridge itself. The sources of volcanoclastics have been determined. The possibility of the existence of Early Eocene submarine volcanoes in the central part of the ridge has been shown. The dynamics of volcanism of the ridge has been compared with the variability of major climatic markers in sediments, indicating the unity of volcanic processes in the region and processes that led to an increase in the index of 13C content in sediments and CO2 content in the atmosphere.

  14. Surficial geologic map of Berrien County, Michigan, and the adjacent offshore area of Lake Michigan

    USGS Publications Warehouse

    Stone, Byron D.; Kincare, Kevin A.; O'Leary, Dennis W.; Newell, Wayne L.; Taylor, Emily M.; Williams, Van S.; Lundstrom, Scott C.; Abraham, Jared E.; Powers, Michael H.

    2017-12-13

    The surficial geologic map of Berrien County, southwestern Michigan (sheet 1), shows the distribution of glacial and postglacial deposits at the land surface and in the adjacent offshore area of Lake Michigan. The geologic map differentiates surficial materials of Quaternary age on the basis of their lithologic characteristics, stratigraphic relationships, and age. Drill-hole information correlated in cross sections provides details of typical stratigraphic sequences that compose one or more penetrated geologic map units. A new bedrock geologic map (on sheet 2) includes contours of the altitude of the eroded top of bedrock and shows the distribution of middle Paleozoic shale and carbonate units in the subcrop. A sediment thickness map (also on sheet 2) portrays the extent of as much as 150 meters of surficial materials that overlie the bedrock surface.The major physical features of the county are related principally to deposits of the last Laurentide ice sheet that advanced and then retreated back through the region from about 19,000 to 14,000 radiocarbon years before present. Glacial and postglacial deposits underlie the entire county; shale bedrock crops out only in the adjacent offshore area on the bottom of Lake Michigan. All glacial deposits and glacial meltwater deposits in Berrien County are related to the late Wisconsinan glacial advances of the Lake Michigan ice lobe and its three regional recessional moraines, which cross the county as three north-northeast-trending belts.From east to west (oldest to youngest), the three moraine belts are known as the Kalamazoo, Valparaiso, and Lake Border morainic systems. The till-ridge morainic systems (Lake Border and local Valparaiso morainic systems) consist of multiple, elongate moraine ridges separated by till plains and lake-bottom plains. Tills in ground and end moraines in Berrien County are distinguished as informal units, and are correlated with three proposed regional till units in southwestern Michigan

  15. Implications of hydrologic variability on the succession of plants in Great Lakes wetlands

    USGS Publications Warehouse

    Wilcox, Douglas A.

    2004-01-01

    Primary succession of plant communities directed toward a climax is not a typical occurrence in wetlands because these ecological systems are inherently dependent on hydrology, and temporal hydrologic variability often causes reversals or setbacks in succession. Wetlands of the Great Lakes provide good examples for demonstrating the implications of hydrology in driving successional processes and for illustrating potential misinterpretations of apparent successional sequences. Most Great Lakes coastal wetlands follow cyclic patterns in which emergent communities are reduced in area or eliminated by high lake levels and then regenerated from the seed bank during low lake levels. Thus, succession never proceeds for long. Wetlands also develop in ridge and swale terrains in many large embayments of the Great Lakes. These formations contain sequences of wetlands of similar origin but different age that can be several thousand years old, with older wetlands always further from the lake. Analyses of plant communities across a sequence of wetlands at the south end of Lake Michigan showed an apparent successional pattern from submersed to floating to emergent plants as water depth decreased with wetland age. However, paleoecological analyses showed that the observed vegetation changes were driven largely by disturbances associated with increased human settlement in the area. Climate-induced hydrologic changes were also shown to have greater effects on plant-community change than autogenic processes. Other terms, such as zonation, maturation, fluctuations, continuum concept, functional guilds, centrifugal organization, pulse stability, and hump-back models provide additional means of describing organization and changes in vegetation; some of them overlap with succession in describing vegetation processes in Great Lakes wetlands, but each must be used in the proper context with regard to short- and long-term hydrologic variability.

  16. Base-flow characteristics of streams in the Valley and Ridge, Blue Ridge, and Piedmont physiographic provinces of Virginia

    USGS Publications Warehouse

    Nelms, D.L.; Harlow, G.E.; Hayes, Donald C.

    1995-01-01

    Growth within the Valley and Ridge, Blue Ridge, and Piedmont Physiographic Provinces of Virginia has focussed concern about allocation of surface-water flow and increased demands on the ground-water resources. The purpose of this report is to (1) describe the base-flow characteristics of streams, (2) identify regional differences in these flow characteristics, and (3) describe, if possible, the potential surface-water and ground-water yields of basins on the basis of the base-flow character- istics. Base-flow characteristics are presented for streams in the Valley and Ridge, Blue Ridge, and Piedmont Physiographic Provinces of Virginia. The provinces are separated into five regions: (1) Valley and Ridge, (2) Blue Ridge, (3) Piedmont/Blue Ridge transition, (4) Piedmont northern, and (5) Piedmont southern. Different flow statistics, which represent streamflows predominantly comprised of base flow, were determined for 217 continuous-record streamflow-gaging stations from historical mean daily discharge and for 192 partial-record streamflow-gaging stations by means of correlation of discharge measurements. Variability of base flow is represented by a duration ratio developed during this investigation. Effective recharge rates were also calculated. Median values for the different flow statistics range from 0.05 cubic foot per second per square mile for the 90-percent discharge on the streamflow-duration curve to 0.61 cubic foot per second per square mile for mean base flow. An excellent estimator of mean base flow for the Piedmont/Blue Ridge transition region and Piedmont southern region is the 50-percent discharge on the streamflow-duration curve, but tends to under- estimate mean base flow for the remaining regions. The base-flow variability index ranges from 0.07 to 2.27, with a median value of 0.55. Effective recharge rates range from 0.07 to 33.07 inches per year, with a median value of 8.32 inches per year. Differences in the base-flow characteristics exist between

  17. Emergence and petrology of the Mendocino Ridge

    NASA Astrophysics Data System (ADS)

    Fisk, Martin R.; Duncan, Robert A.; Fox, Christopher G.; Witter, Jeffrey B.

    1993-11-01

    The Mendocino Fracture Zone, a 3,000-km-long transform fault, extends from the San Andreas Fault at Cape Mendocino, California due west into the central Pacific basin. The shallow crest of this fracture zone, known as the Mendocino Ridge, rises to within 1,100 m of the sea surface at 270 km west of the California Coast. Rounded basalt pebbles and cobbles, indicative of a beach environment, are the dominant lithology at two locations on the crest of Mendocino Ridge and a40Ar/39 Ar incremental heating age of 11.0 ± 1.0 million years was determined for one of the these cobbles. This basalt must have been erupted on the Gorda Ridge because the crust immediately to the south of the fracture zone is older than 27 Ma. This age also implies that the crest of Mendocino Ridge was at sea level and would have blocked Pacific Ocean eastern boundary currents and affected the climate of the North American continent at some time since the late Miocene. Basalts from the Mendocino Fracture Zone (MFZ) are FeTi basalts similar to those commonly found at intersections of mid-ocean ridges and fracture zones. These basalts are chemically distinct from the nearby Gorda Ridge but they could have been derived from the same mantle source as the Gorda Ridge basalts. The location of the 11 Ma basalt suggests that Mendocino Ridge was transferred from the Gorda Plate to the Pacific Plate and the southern end of Gorda Ridge was truncated by a northward jump in the transform fault of MFZ.

  18. Summary and interpretation of dye-tracer tests to investigate the hydraulic connection of fractures at a ridge-and-valley-wall site near Fishtrap Lake, Pike County, Kentucky

    USGS Publications Warehouse

    Taylor, Charles J.

    1994-01-01

    Dye-tracer tests were done during 1985-92 to investigate the hydraulic connection between fractures in Pennsylvanian coal-bearing strata at a ridge-and-valley-wall site near Fishtrap Lake, Pike County, Ky. Fluorescent dye was injected into a core hole penetrating near-surface and mining-induced fractures near the crest of the ridge. The rate and direction of migration of dye in the subsurface were determined by measuring the relative concentration of dye in water samples collected from piezometers completed in conductive fracture zones and fractured coal beds at various stratigraphic horizons within the ridge. Dye-concentration data and water-level measurements for each piezometer were plotted as curves on dye-recovery hydrographs. The dye-recovery hydrographs were used to evaluate trends in the fluctuation of dye concentrations and hydraulic heads in order to identify geologic and hydrologic factors affecting the subsurface transport of dye. The principal factors affecting the transport of dye in the subsurface hydrologic system were determined to be (1) the distribution, interconnection, and hydraulic properties of fractures; (2) hydraulic-head conditions in the near-fracture zone at the time of dye injection; and (3) subsequent short- and long-term fluctuations in recharge to the hydrologic system. In most of the dye-tracer tests, dye-recovery hydrographs are characterized by complex, multipeaked dye-concentration curves that are indicative of a splitting of dye flow as ground water moved through fractures. Intermittent dye pulses (distinct upward spikes in dye concentration) mark the arrivals of dye-labeled water to piezometers by way of discrete fracture-controlled flow paths that vary in length, complexity, and hydraulic conductivity. Dye injections made during relatively high- or increasinghead conditions resulted in rapid transport of dye (within several days or weeks) from near-surf ace fractures to piezometers. Injections made during relatively low- or

  19. Hydrothermal Activity Along the Central Indian Ridge: Ridges, Hotspots and Philately.

    NASA Astrophysics Data System (ADS)

    German, C. R.; Connelly, D. P.; Evans, A. J.; Murton, B. J.; Curewitz, D.; Okino, K.; Statham, P. J.; Parson, L. M.

    2001-12-01

    The global mid-ocean ridge crest extends 50-60,000km and the majority remains unexplored for hydrothermal activity. Even those areas which are reasonably familiar continue to spring surprises (e.g. the "Lost City" site found in late 2000). Within the confines of conceivable research budgets, therefore, choosing new areas for investigation and exploration demands an intelligent approach, beyond flicking through holiday brochures or identifying missing entries for the John Edmond Memorial Stamp Collection. With that caveat, the Southampton Oceanography Centre led a 10-week expedition to the Central Indian Ridge, earlier this year, based in and around Mauritius. During cruise CD127 (23 April-23 May) we conducted a systematic investigation of the ridge crest (seafloor and overlying water column) between 18 deg 16 min and 20 deg 49 min South. We chose this area to investigate the distribution of hydrothermal activity both close to, and away from, that section of the ridge crest which continues to reflect past influence of the migrating Rodrigues hot-spot. Our hypothesis was that the high incidence of hydrothermal activity we had located previously, near the Azores Triple Junction, may result from waning influence of the Azores Hot-Spot nearby and that similar effects might be found resulting from interaction of the CIR with the Rodrigues hot-spot. The primary scientific package we employed was the SOC's TOBI deep-tow sidescan vehicle, now up-graded with an extra Light Scattering Sensor string. In concert, this instrumentation allowed us to prospect for particle-laden hydrothermal plumes in the water column overlying the ridge-crest, in real-time, whilst simultaneously acquiring high-resolution sidescan images of the underlying seafloor. Using this approach, particle-rich anomalies were observed at 5 locations along ca. 300km of surveyed ridge-crest, including 4 sites all within the extended (hot-spot influenced) segment 15, which stretches from 18 deg 45 to 20 deg 14

  20. Dark and Bright Ridges on Europa

    NASA Technical Reports Server (NTRS)

    1998-01-01

    This high-resolution image of Jupiter's moon Europa, taken by NASA's Galileo spacecraft camera, shows dark, relatively smooth region at the lower right hand corner of the image which may be a place where warm ice has welled up from below. The region is approximately 30 square kilometers in area. An isolated bright hill stands within it. The image also shows two prominent ridges which have different characteristics; youngest ridge runs from left to top right and is about 5 kilometers in width (about 3.1 miles). The ridge has two bright, raised rims and a central valley. The rims of the ridge are rough in texture. The inner and outer walls show bright and dark debris streaming downslope, some of it forming broad fans. This ridge overlies and therefore must be younger than a second ridge running from top to bottom on the left side of the image. This dark 2 km wide ridge is relatively flat, and has smaller-scale ridges and troughs along its length.

    North is to the top of the picture, and the sun illuminates the surface from the upper left. This image, centered at approximately 14 degrees south latitude and 194 degrees west longitude, covers an area approximately 15 kilometers by 20 kilometers (9 miles by 12 miles). The resolution is 26 meters (85 feet) per picture element. This image was taken on December 16, 1997 at a range of 1300 kilometers (800 miles) by Galileo's solid state imaging system.

    The Jet Propulsion Laboratory, Pasadena, CA manages the Galileo mission for NASA's Office of Space Science, Washington, DC. JPL is an operating division of California Institute of Technology (Caltech).

    This image and other images and data received from Galileo are posted on the World Wide Web, on the Galileo mission home page at URL http://www.jpl.nasa.gov/ galileo.

  1. Comprehensive integrated planning: A process for the Oak Ridge Reservation, Oak Ridge, Tennessee

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    NONE

    1998-05-01

    The Oak Ridge Comprehensive Integrated Plan is intended to assist the US Department of Energy (DOE) and contractor personnel in implementing a comprehensive integrated planning process consistent with DOE Order 430.1, Life Cycle Asset Management and Oak Ridge Operations Order 430. DOE contractors are charged with developing and producing the Comprehensive Integrated Plan, which serves as a summary document, providing information from other planning efforts regarding vision statements, missions, contextual conditions, resources and facilities, decision processes, and stakeholder involvement. The Comprehensive Integrated Plan is a planning reference that identifies primary issues regarding major changes in land and facility use andmore » serves all programs and functions on-site as well as the Oak Ridge Operations Office and DOE Headquarters. The Oak Ridge Reservation is a valuable national resource and is managed on the basis of the principles of ecosystem management and sustainable development and how mission, economic, ecological, social, and cultural factors are used to guide land- and facility-use decisions. The long-term goals of the comprehensive integrated planning process, in priority order, are to support DOE critical missions and to stimulate the economy while maintaining a quality environment.« less

  2. Influence of near-surface stratigraphy on coastal landslides at Sleeping Bear Dunes National Lakeshore, Lake Michigan, USA

    USGS Publications Warehouse

    Barnhardt, W.A.; Jaffe, B.E.; Kayen, R.E.; Cochrane, G.R.

    2004-01-01

    Lake-level change and landslides are primary controls on the development of coastal environments along the coast of northeastern Lake Michigan. The late Quaternary geology of Sleeping Bear Dunes National Lakeshore was examined with high-resolution seismic reflection profiles, ground-penetrating radar (GPR), and boreholes. Based on sequence-stratigraphic principles, this study recognizes ten stratigraphic units and three major unconformities that were formed by late Pleistocene glaciation and postglacial lake-level changes. Locally high sediment supply, and reworking by two regressions and a transgression have produced a complex stratigraphy that is prone to episodic failure. In 1995, a large landslide deposited approximately 1 million m3 of sediment on the lake floor. The highly deformed landslide deposits, up to 18 m thick, extend 3-4 km offshore and unconformably overlie well-stratified glacial and lacustrine sediment. The landslide-prone bluff is underlain by channel-fill deposits that are oriented nearly perpendicular to the shoreline. The paleochannels are at least 10 m deep and 400 m wide and probably represent stream incision during a lake-level lowstand about 10.3 ka B.P. The channels filled with sediment during the subsequent transgression and lake-level highstand, which climaxed about 4.5 ka B.P. As lake level fell from the highstand, the formation of beach ridges and sand dunes sealed off the channel and isolated a small inland lake (Glen Lake), which lies 5 m above the level of Lake Michigan and may be a source of piped groundwater. Our hypothesis is that the paleochannels act as conduits for pore water flow, and thereby locally reduce soil strength and promote slope failure.

  3. Does Graft Particle Type and Size Affect Ridge Dimensional Changes After Alveolar Ridge Split Procedure?

    PubMed

    Kheur, Mohit G; Kheur, Supriya; Lakha, Tabrez; Jambhekar, Shantanu; Le, Bach; Jain, Vinay

    2018-04-01

    The absence of an adequate volume of bone at implant sites requires augmentation procedures before the placement of implants. The aim of the present study was to assess the ridge width gain with the use of allografts and biphasic β-tricalcium phosphate with hydroxyapatite (alloplast) in ridge split procedures, when each were used in small (0.25 to 1 mm) and large (1 to 2 mm) particle sizes. A randomized controlled trial of 23 subjects with severe atrophy of the mandible in the horizontal dimension was conducted in a private institute. The patients underwent placement of 49 dental implants after a staged ridge split procedure. The patients were randomly allocated to alloplast and allograft groups (predictor variable). In each group, the patients were randomly assigned to either small graft particle or large graft particle size (predictor variable). The gain in ridge width (outcome variable) was assessed before implant placement. A 2-way analysis of variance test and the Student unpaired t test were used for evaluation of the ridge width gain between the allograft and alloplast groups (predictor variable). Differences were considered significant if P values were < .05. The sample included 23 patients (14 men and 9 women). The patients were randomly allocated to the alloplast (n = 11) or allograft (n = 12) group before the ridge split procedure. In each group, they were assigned to a small graft particle or large graft particle size (alloplast group, small particle in 5 and large particle size in 6 patients; allograft group, small particle in 6 and large particle size in 6). A statistically significant difference was observed between the 2 graft types. The average ridge width gain was significantly greater in the alloplast group (large, 4.40 ± 0.24 mm; small, 3.52 ± 0.59 mm) than in the allograft group (large, 3.82 ± 0.19 mm; small, 2.57 ± 0.16 mm). For both graft types (alloplast and allograft), the large particle size graft resulted in a

  4. Compressive strain in Lunae Planum-shortening across wrinkle ridges

    NASA Technical Reports Server (NTRS)

    Plescia, J. B.

    1991-01-01

    Wrinkle ridges have long been considered to be structural or structurally controlled features. Most, but not all, recent studies have converged on a model in which wrinkle ridges are structural features formed under compressive stress; the deformation being accommodated by faulting and folding. Given that wrinkle ridges are compressive tectonic features, an analysis of the associated shortening and strain provides important quantitative information about local and regional deformation. Lunae Planum is dominated by north-south trending ridges extending from Kasei Valles in the north to Valles Marineris in the south. To quantify the morphometric character, a photoclinometric study was undertaken for ridges on Lunae Planum using the Davis and Soderblom. More than 25 ridges were examined between long. 57 and 80 deg, lat. 5 to 25 deg N. For each ridge, several profiles were obtained along its length. Ridge width, total relief, and elevation offset were measured for each ridge. Analyses are given.

  5. Ridges and scarps in the equatorial belt of Mars

    USGS Publications Warehouse

    Lucchitta, B.K.; Klockenbrink, J.L.

    1981-01-01

    The morphology and distribution of ridges and scarps on Mars in the ?? 30?? latitude belt were investigated. Two distinct types of ridges were recognized. The first is long and linear, resembling mare ridges on the Moon; it occurs mostly in plains areas. The other is composed of short, anastomosing segments and occurs mostly in ancient cratered terrain and intervening plateaus. Where ridges are eroded, landscape configurations suggest that they are located along regional structures. The age of ridges is uncertain, but some are as young as the latest documented volcanic activity on Mars. The origins of ridges are probably diverse-they may result from wrinkling due to compression or from buckling due to settling over subsurface structures. The similar morphologic expressions of ridge types of various origins may be related to a similar deformation mechanism caused by two main factors: (1) most ridges are developed in thick layers of competent material and (2) ridges formed under stresses near a free surface. ?? 1981 D. Reidel Publishing Co.

  6. Geophysical Characteristics of the Australian-Antarctic Ridge

    NASA Astrophysics Data System (ADS)

    Kim, S. S.; Lin, J.; Park, S. H.; Choi, H.; Lee, S. M.

    2014-12-01

    Between 2011 and 2013, the Korea Polar Research Institute (KOPRI) conducted three consecutive geologic surveys at the little explored eastern ends of the Australian-Antarctic Ridge (AAR) to characterize the tectonics, geochemistry, and hydrothermal activity of this intermediate spreading system. Using the Korean icebreaker R/V Araon, the multi-disciplinary research team collected bathymetry, gravity, magnetics, and rock and water column samples. In addition, Miniature Autonomous Plume Recorders (MAPRs) were deployed at wax-core rock sampling sites to detect the presence of active hydrothermal vents. Here we present a detailed analysis of a 300-km-long supersegment of the AAR to quantify the spatial variations in ridge morphology and robust axial and off-axis volcanisms. The ridge axis morphology alternates between rift valleys and axial highs within relatively short ridge segments. To obtain a geological proxy for regional variations in magma supply, we calculated residual mantle Bouguer gravity anomalies (RMBA), gravity-derived crustal thickness, and residual topography for seven sub-segments. The results of the analyses revealed that the southern flank of the AAR is associated with shallower seafloor, more negative RMBA, thicker crust, and/or less dense mantle than the conjugate northern flank. Furthermore, this north-south asymmetry becomes more prominent toward the KR1 supersegment of the AAR. The axial topography of the KR1 supersegment exhibits a sharp transition from axial highs at the western end to rift valleys at the eastern end, with regions of axial highs being associated with more magma supply as indicated by more negative RMBA. We also compare and contrast the characteristics of the AAR supersegment with that of other ridges of intermediate spreading rates, including the Juan de Fuca Ridge, Galápagos Spreading Center, and Southeast Indian Ridge west of the Australian-Antarctic Discordance, to investigate the influence of ridge-hotspot interaction on

  7. Volcanism and hydrothermalism on a hotspot-influenced ridge: Comparing Reykjanes Peninsula and Reykjanes Ridge, Iceland

    NASA Astrophysics Data System (ADS)

    Pałgan, Dominik; Devey, Colin W.; Yeo, Isobel A.

    2017-12-01

    Current estimates indicate that the number of high-temperature vents (one of the primary pathways for the heat extraction from the Earth's mantle) - at least 1 per 100 km of axial length - scales with spreading rate and should scale with crustal thickness. But up to present, shallow ridge axes underlain by thick crust show anomalously low incidences of high-temperature activity. Here we compare the Reykjanes Ridge, an abnormally shallow ridge with thick crust and only one high-temperature vent known over 900 km axial length, to the adjacent subaerial Reykjanes Peninsula (RP), which is characterized by high-temperature geothermal sites confined to four volcanic systems transected by fissure swarms with young (Holocene) volcanic activity, multiple faults, cracks and fissures, and continuous seismic activity. New high-resolution bathymetry (gridded at 60 m) of the Reykjanes Ridge between 62°30‧N and 63°30‧N shows seven Axial Volcanic Ridges (AVR) that, based on their morphology, geometry and tectonic regime, are analogues for the volcanic systems and fissure swarms on land. We investigate in detail the volcano-tectonic features of all mapped AVRs and show that they do not fit with the previously suggested 4-stage evolution model for AVR construction. Instead, we suggest that AVR morphology reflects the robust or weak melt supply to the system and two (or more) eruption mechanisms may co-exist on one AVR (in contrast to 4-stage evolution model). Our interpretations indicate that, unlike on the Reykjanes Peninsula, faults on and around AVRs do not cluster in orientation domains but all are subparallel to the overall strike of AVRs (orthogonal to spreading direction). High abundance of seamounts shows that the region centered at 62°47‧N and 25°04‧W (between AVR-5 and -6) is volcanically robust while the highest fault density implies that AVR-1 and southern part of AVR-6 rather undergo period of melt starvation. Based on our observations and interpretations we

  8. 77 FR 41686 - Safety Zone; Sheffield Lake Fireworks, Lake Erie, Sheffield Lake, OH

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-07-16

    ...-AA00 Safety Zone; Sheffield Lake Fireworks, Lake Erie, Sheffield Lake, OH AGENCY: Coast Guard, DHS. ACTION: Temporary final rule. SUMMARY: The Coast Guard is establishing a temporary safety zone on Lake Erie, Sheffield Lake, OH. This safety zone is intended to restrict vessels from a portion of Lake Erie...

  9. Paired moraine-dammed lakes: a key landform for glaciated high mountain areas in the tropical Andes of Peru

    NASA Astrophysics Data System (ADS)

    Iturrizaga, Lasafam

    2016-04-01

    The tropical mountain range of the Cordillera Blanca hosts one of the main concentrations of proglacial lakes in high-mountain settings worldwide, which have formed as a result of the dominant trend of modern glacier retreat. Based on empirical data from field research in over 20 valleys and the analysis of air and satellite images, a genetic classification of major lake types with their barriers and a generalized model for the distribution of the present lakes and paleolakes was set up. The origin of the lakes and their recurrent distribution pattern are associated with the individual stages of the Pleistocene to modern glaciation and their corresponding geomorphological landforms. Characteristic repetitive moraine sequences are found in the upper parts of numerous valleys of the Cordillera Blanca. In terms of the spatial arrangement of the lake types, combined lakes are classified as a distinct composite lake type. These lakes occur at nearly the same elevation or at successively lower elevations, and form characteristic lake sequences of two or more lakes. They may occur as multi-moraine-dammed lakes or mixed combined lakes such as moraine-rock-dammed lakes or multi-debris-dammed lakes. From special interest are in this study the paired moraine-dammed lakes (e.g. Lagunas Qoyllurcochas, Lagunas Safuna Alta and Baja). They are composed of the Great Endmoraine (GEM), primarily formed during the Little Ice Age and earlier, and the pre-GEM, formed during the Holocene. Both moraines are located in rather close vicinity to each other at a distance of 1-3 km. In contrast to the prominent sharp-crested GEM, the pre-GEM is a low-amplitude end-moraine complex, which usually does not exceed a few meters to tens of meters in height. The latter is often composed of several inserted moraine ridges or an irregular hummocky moraine landscape. It is argued here that the process of formation of these combined lakes is mainly controlled by a combination of distinct topographical

  10. Ridges on Europa

    NASA Image and Video Library

    1997-12-18

    This view of Jupiter's moon Europa shows a portion of the surface that has been highly disrupted by fractures and ridges. This picture covers an area about 238 kilometers (150 miles) wide by 225 kilometers (140 miles), or about the distance between Los Angeles and San Diego. Symmetric ridges in the dark bands suggest that the surface crust was separated and filled with darker material, somewhat analogous to spreading centers in the ocean basins of Earth. Although some impact craters are visible, their general absence indicates a youthful surface. The youngest ridges, such as the two features that cross the center of the picture, have central fractures, aligned knobs, and irregular dark patches. These and other features could indicate cryovolcanism, or processes related to eruption of ice and gases. This picture, centered at 16 degrees south latitude, 196 degrees west longitude, was taken at a distance of 40,973 kilometers (25,290 mi) on November 6, 1996 by the Galileo spacecraft solid state imaging television camera onboard the Galileo spacecraft during its third orbit around Jupiter. http://photojournal.jpl.nasa.gov/catalog/PIA00518

  11. Tectonics of the baikal rift deduced from volcanism and sedimentation: a review oriented to the Baikal and Hovsgol lake systems.

    PubMed

    Ivanov, Alexei V; Demonterova, Elena I

    2009-01-01

    As known from inland sedimentary records, boreholes, and geophysical data, the initiation of the Baikal rift basins began as early as the Eocene. Dating of volcanic rocks on the rift shoulders indicates that volcanism started later, in the Early Miocene or probably in the Late Oligocene. Prominent tectonic uplift took place at about 20 Ma, but information (from both sediments and volcanics) on the initial stage of the rifting is scarce and incomplete. A comprehensive record of sedimentation derived from two stacked boreholes drilled at the submerged Akademichesky ridge indicates that the deep freshwater Lake Baikal existed for at least 8.4 Ma, while the exact formation of the lake in its roughly present-day shape and volume is unknown. Four important events of tectonic/environmental changes at about approximately 7, approximately 5, approximately 2.5, and approximately 0.1 Ma are seen in that record. The first event probably corresponds to a stage of rift propagation from the historical center towards the wings of the rift system. Rifting in the Hovsgol area was initiated at about this time. The event of ~5 Ma is a likely candidate for the boundary between slow and fast stages of rifting. It is reflected in a drastic change of sedimentation rate due to isolation of the Akademichesky ridge from the central and northern Lake Baikal basins. The youngest event of 0.1 Ma is reflected by the (87)0Sr/ (86)Sr ratio increase in Lake Baikal waters and probably related to an increasing rate of mountain growth (and hence erosion) resulting from glacial rebounding. The latter is responsible for the reorganization of the outflow pattern with the termination of the paleo-Manzurka outlet and the formation of the Angara outlet. The event of approximately 2.5 Ma is reflected in the decrease of the (87)Sr/(86)Sr and Na/Al ratios in Lake Baikal waters. We suggest that it is associated with a decrease of the dust load due to a reorganization of the atmospheric circulations in Mainland

  12. Limnology of the Green Lakes Valley: Phytoplankton ecology and dissolved organic matter biogeochemistry at a long-term ecological research site

    USGS Publications Warehouse

    Miller, Matthew P.; McKnight, Diane M.

    2015-01-01

    Background: Surface waters are the lowest points in the landscape, and therefore serve as excellent integrators and indicators of changes taking place in the surrounding terrestrial and atmospheric environment.Aims: Here we synthesise the findings of limnological studies conducted during the past 15 years in streams and lakes in the Green Lakes Valley, which is part of the Niwot Ridge Long-term Ecological Research (LTER) Site.Methods: The importance of these studies is discussed in the context of aquatic ecosystems as indicators, integrators, and regulators of environmental change. Specifically, investigations into climatic, hydrologic, and nutrient controls on present-day phytoplankton, and historical diatom, community composition in the alpine lake, Green Lake 4, are reviewed. In addition, studies of spatial and temporal patterns in dissolved organic matter (DOM) biogeochemistry and reactive transport modelling that have taken place in the Green Lakes Valley are highlighted.Results and conclusions: The findings of these studies identify specific shifts in algal community composition and DOM biogeochemistry that are indicative of changing environmental conditions and provide a framework for detecting future environmental change in the Green Lakes Valley and in other alpine watersheds. Moreover, the studies summarised here demonstrate the importance of long-term monitoring programmes such as the LTER programme.

  13. Petrological systematics of mid-ocean ridge basalts: Constraints on melt generation beneath ocean ridges

    NASA Astrophysics Data System (ADS)

    Langmuir, Charles H.; Klein, Emily M.; Plank, Terry

    Mid-ocean ridge basalts (MORB) are a consequence of pressure-release melting beneath ocean ridges, and contain much information concerning melt formation, melt migration and heterogeneity within the upper mantle. MORB major element chemical systematics can be divided into global and local aspects, once they have been corrected for low pressure fractionation and interlaboratory biases. Regional average compositions for ridges unaffected by hot spots ("normal" ridges) can be used to define the global correlations among normalized Na2O, FeO, TiO2 and SiO2 contents, CaO/Al2O3 ratios, axial depth and crustal thickness. Back-arc basins show similar correlations, but are offset to lower FeO and TiO2 contents. Some hot spots, such as the Azores and Galapagos, disrupt the systematics of nearby ridges and have the opposite relationships between FeO, Na2O and depth over distances of 1000 km. Local variations in basalt chemistry from slow- and fast-spreading ridges are distinct from one another. On slow-spreading ridges, correlations among the elements cross the global vector of variability at a high angle. On the fast-spreading East Pacific Rise (EPR), correlations among the elements are distinct from both global and slow-spreading compositional vectors, and involve two components of variation. Spreading rate does not control the global correlations, but influences the standard deviations of axial depth, crustal thickness, and MgO contents of basalts. Global correlations are not found in very incompatible trace elements, even for samples far from hot spots. Moderately compatible trace elements for normal ridges, however, correlate with the major elements. Trace element systematics are significantly different for the EPR and the mid-Atlantic Ridge (MAR). Normal portions of the MAR are very depleted in REE, with little variability; hot spots cause large long wavelength variations in REE abundances. Normal EPR basalts are significantly more enriched than MAR basalts from normal

  14. Lake trout rehabilitation in Lake Ontario

    USGS Publications Warehouse

    Elrod, Joseph H.; O'Gorman, Robert; Schneider, Clifford P.; Eckert, Thomas H.; Schaner, Ted; Bowlby, James N.; Schleen, Larry P.

    1995-01-01

    Attempts to maintain the native lake trout (Salvelinus namaycush) population in Lake Ontario by stocking fry failed and the species was extirpated by the 1950s. Hatchery fish stocked in the 1960s did not live to maturity because of sea lamprey (Petromyzon marinus) predation and incidental commercial harvest. Suppression of sea lampreys began with larvicide treatments of Lake Ontario tributaries in 1971 and was enhanced when the tributaries of Oneida Lake and Lake Erie were treated in the 1980s. Annual stocking of hatchery fish was resumed with the 1972 year class and peaked at about 1.8 million yearlings and 0.3 million fingerlings from the 1985–1990 year classes. Survival of stocked yearlings declined over 50% in the 1980 s and was negatively correlated with the abundance of lake trout > 550 mm long (r = −0.91, P < 0.01, n = 12). A slot length limit imposed by the State of New York for the 1988 fishing season reduced angler harvest. Angler harvest in Canadian waters was 3 times higher in eastern Lake Ontario than in western Lake Ontario. For the 1977–1984 year classes, mean annual survival rate of lake trout age 6 and older was 0.45 (range: 0.35–0.56). In U.S. waters during 1985–1992, the total number of lake trout harvested by anglers was about 2.4 times greater than that killed by sea lampreys. The number of unmarked lake trout < 250 mm long in trawl catches in 1978–1992 was not different from that expected due to loss of marks and failure to apply marks at the hatchery, and suggested that recruitment of naturally-produced fish was nil. However, many of the obstacles which may have impeded lake trout rehabilitation in Lake Ontario during the 1980s are slowly being removed, and there are signs of a general ecosystem recovery. Significant recruitment of naturally produced lake trout by the year 2000, one interim objective of the rehabilitation plan for the Lake, may be achieved.

  15. Lake level variability in Silver Lake, Michigan: a response to fluctuations in lake levels of Lake Michigan

    USGS Publications Warehouse

    Fisher, Timothy G.; Loope, Walter L.

    2004-01-01

    Sediment from Silver Lake, Michigan, can be used to constrain the timing and elevation of Lake Michigan during the Nipissing transgression. Silver Lake is separated from Lake Michigan by a barrier/dune complex and the Nipissing, Calumet, and Glenwood shorelines of Lake Michigan are expressed landward of this barrier. Two Vibracores were taken from the lake in February 2000 and contain pebbly sand, sand, buried soils, marl, peat, and sandy muck. It is suggested here that fluctuations in the level of Lake Michigan are reflected in Silver Lake since the Chippewa low phase, and possibly at the end of the Algonquin phase. An age of 12,490 B.P. (10,460±50 14C yrs B.P.) on wood from a buried Entisol may record the falling Algonquin phase as the North Bay outlet opened. A local perched water table is indicated by marl deposited before 7,800 B.P. and peat between 7,760-7,000 B.P. when Lake Michigan was at the low elevation Chippewa phase. Continued deepening of the lake is recorded by the transition from peat to sandy muck at 7,000 B.P. in the deeper core, and with the drowning of an Inceptisol nearly 3 m higher at 6,410 B.P. in the shallower core. A rising groundwater table responding to a rising Lake Michigan base level during the Nipissing transgression, rather than a response to mid-Holocene climate change, explains deepening of Silver Lake. Sandy muck was deposited continually in Silver Lake between Nipissing and modern time. Sand lenses within the muck are presumed to be eolian in origin, derived from sand dunes advancing into the lake on the western side of the basin.

  16. Fire-climate-human interactions during the postglacial period at Sunrise Ridge, Mount Rainier National Park, Washington (USA)

    NASA Astrophysics Data System (ADS)

    Walsh, Megan K.; Lukens, Michael L.; McCutcheon, Patrick T.; Burtchard, Greg C.

    2017-12-01

    With the creation of Mount Rainier National Park (MORA) in 1899 came the active management of the park's landscapes and a heavy emphasis on fire suppression. Today, managers at MORA seek to better manage current fire activity; however, this requires an improved understanding of past fire activity on the mountain. In this study high-resolution macroscopic charcoal analysis and pollen analysis of lake sediment records was used to reconstruct the postglacial fire and vegetation history for the Sunrise Ridge area of MORA. Fire activity was lowest during the Late Glacial when vegetation was sparse and climate was cool and dry. Fire activity increased during the early Holocene as the regional climate warmed and dried, and burnable biomass became more abundant. Fire activity continued to increase into the middle Holocene (until ca. 6600 cal yr BP) even as the regional climate became wetter and eventually cooler; the modern-day mesic forest and subalpine meadow landscapes of the park established at this time. Fire activity was generally highest and mean fire return intervals were lowest on Sunrise Ridge during the late Holocene, and are consistent with tree-ring based estimates of fire frequency. The similarity between the Sunrise Ridge and other paleofire records in the Pacific Northwest suggests that broad-scale climatic shifts, such as the retreat of the Cordilleran ice sheet and changes in annual insolation, as well as increased interannual climate variability (i.e., drought) particularly in the middle to late Holocene, were responsible for changes in fire activity during the postglacial period. However, abundant and increasing archaeological evidence from Sunrise Ridge during the middle to late Holocene suggests that humans may have also influenced the landscape at this time. It is likely that fires will continue to increase at MORA as drought becomes a more frequent occurrence in the Pacific Northwest.

  17. How Fast Do Europa's Ridges Grow?

    NASA Astrophysics Data System (ADS)

    Melosh, H. J.; Turtle, E. P.; Freed, A. M.

    2017-11-01

    We demonstrate with our incremental wedging model of ridge formation that ridges must grow in 5000 years or less to prevent their material flowing down an underlying warm ice channel. This conclusion holds for other models as well.

  18. Mantle plume capture, anchoring and outflow during ridge interaction

    NASA Astrophysics Data System (ADS)

    Gibson, S. A.; Richards, M. A.; Geist, D.

    2015-12-01

    Geochemical and geophysical studies have shown that >40% of the world's mantle plumes are currently interacting with the global ridge system and such interactions may continue for up to 180 Myr[1]. At sites of plume-ridge interaction up to 1400 km of the spreading centre is influenced by dispersed plume material but there are few constraints on how and where the ridge-ward transfer of deep-sourced material occurs, and also how it is sustained over long time intervals. Galápagos is an archetypal example of an off-axis plume and sheds important light on these mechanisms. The Galápagos plume stem is located ~200 km south of the spreading axis and its head influences 1000 km of the ridge. Nevertheless, the site of enriched basalts, greatest crustal thickness and elevated topography on the ridge, together with active volcanism in the archipelago, correlate with a narrow zone (~150 km) of low-velocity, high-temperature mantle that connects the plume stem and ridge at depths of ~100 km[2]. The enriched ridge basalts contain a greater amount of partially-dehydrated, recycled oceanic crust than basalts elsewhere on the spreading axis, or indeed basalts erupted in the region between the plume stem and ridge. The presence of these relatively volatile-rich ridge basalts requires flow of plume material below the peridotite solidus (i.e.>80 km). We propose a 2-stage model for the development and sustainment of a confined zone of deep ridge-ward plume flow. This involves initial on-axis capture and establishment of a sub-ridge channel of plume flow. Subsequent anchoring of the plume stem to a contact point on the ridge during axis migration results in confined ridge-ward flow of plume material via a deep network of melt channels embedded in the normal spreading and advection of the plume head[2]. Importantly, sub-ridge flow is maintained. The physical parameters and styles of mantle flow we have defined for Galápagos are less-well known at other sites of plume-ridge

  19. Microplastic pollution in lakes and lake shoreline sediments - A case study on Lake Bolsena and Lake Chiusi (central Italy).

    PubMed

    Fischer, Elke Kerstin; Paglialonga, Lisa; Czech, Elisa; Tamminga, Matthias

    2016-06-01

    Rivers and effluents have been identified as major pathways for microplastics of terrestrial sources. Moreover, lakes of different dimensions and even in remote locations contain microplastics in striking abundances. This study investigates concentrations of microplastic particles at two lakes in central Italy (Lake Bolsena, Lake Chiusi). A total number of six Manta Trawls have been carried out, two of them one day after heavy winds occurred on Lake Bolsena showing effects on particle distribution of fragments and fibers of varying size categories. Additionally, 36 sediment samples from lakeshores were analyzed for microplastic content. In the surface waters 2.68 to 3.36 particles/m(3) (Lake Chiusi) and 0.82 to 4.42 particles/m(3) (Lake Bolsena) were detected, respectively. Main differences between the lakes are attributed to lake characteristics such as surface and catchment area, depth and the presence of local wind patterns and tide range at Lake Bolsena. An event of heavy winds and moderate rainfall prior to one sampling led to an increase of concentrations at Lake Bolsena which is most probable related to lateral land-based and sewage effluent inputs. The abundances of microplastic particles in sediments vary from mean values of 112 (Lake Bolsena) to 234 particles/kg dry weight (Lake Chiusi). Lake Chiusi results reveal elevated fiber concentrations compared to those of Lake Bolsena what might be a result of higher organic content and a shift in grain size distribution towards the silt and clay fraction at the shallow and highly eutrophic Lake Chiusi. The distribution of particles along different beach levels revealed no significant differences. Copyright © 2016 Elsevier Ltd. All rights reserved.

  20. Rise and fall of a small ice-dammed lake - Role of deglaciation processes and morphology

    NASA Astrophysics Data System (ADS)

    Nehyba, Slavomír; Hanáček, Martin; Engel, Zbyněk; Stachoň, Zdeněk

    2017-10-01

    A small ice-dammed lake, which developed along the margin of Nordenskiöldbreen on the northern coast of Adolfbukta, (central Spitsbergen, Svalbard) has been studied by a combination of facies analysis, ground penetrating radar, analysis of photos and satellite imagery, and by surface mapping by Unmanned Aerial Vehicle (drone). The lake existed between the years 1990-2012 and occupied two partial depressions in the bedrock, separated by a bedrock ridge for the dominant period of its history. Whereas the eastern depression was almost completely infilled due to direct fluvial input, the western depression revealed only thin sedimentary cover and was dotted from the eastern depression by an outflow of surficial waters. Gilbert delta deposits with typical tripartite zones of topset, foreset and bottomset were recognised in the eastern depression. Topset was comprised by deposits of a braided river. Foreset is formed by deposits of sediment gravity flows (turbidity currents and debris flows). Bottomset is represented by alternating suspension deposits and deposits of hyperpycnal underflows (low-density turbidity currents). The ruling factors of the evolution of the delta were glacier retreat, bedrock morphology, both affecting the relative lake level, and the rate of sediment delivery. Glacier retreat over stepped and inclined bedrock morphology led to delta prograding and downstepping. The recognised fluvio-deltaic terraces revealed four lake level falls followed by fluvial downcutting, erosion and redeposition of the older deltaic/lake deposits, the shifting of the lake's position towards the damming glacier and the transition of the sediment input in the same direction. The termination of the lake was a result of further glacier retreat and the opening of subglacial drainage.

  1. Mineral resources of the Devil's Garden Lava Bed, Squaw Ridge Lava Bed, and Four Craters Lava Bed Wilderness Study Areas, Lake County, Oregon

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Keith, W.J.; King, H.D.; Gettings, M.E.

    1988-01-01

    The Devel's Garden lava Bed, Squaw Ridge Lava Bed, and Four Craters Lava Bed Wilderness Study Areas include approximately 70,940 acres and are underlain entirely by Pleistocene or Holocene lava flows and associated sediments. There is no evidence of hydrothermal alteration in the study areas. No resources were identified in the study areas, but there is low potential for perlite resources in the southern part of the Devil's Garden Lava Bed and the northern half of the Squaw Ridge Lava Bed areas. All three study areas have low potential for geothermal resources and for oil and gas resources.

  2. Stress history and geotechnical properties of sediment from the Cape Fear Diapir, Blake Ridge Diapir, and Blake Ridge

    USGS Publications Warehouse

    Winters, W.J.

    2000-01-01

    Geotechnical properties of sediment from Ocean Drilling Program Leg 164 are presented as: (1) normalized shipboard strength ratios from the Cape Fear Diapir, the Blake Ridge Diapir, and the Blake Ridge; and (2) Atterberg limit, vane shear strength, pocket-penetrometer strength, and constant-rate-of-strain consolidation results from Hole 995A, located on the Blake Ridge. This study was conducted to understand the stress history in a region characterized by high sedimentation rates and the presence of gas hydrates. Collectively, the results indicate that sediment from the Blake Ridge exhibits significant underconsolidated behavior, except near the seafloor. At least 10 m of additional overburden was removed by erosion or mass wasting at Hole 993A on the Cape Fear Diapir, compared to nearby sites.

  3. Lake whitefish and lake herring population structure and niche in ten south-central Ontario lakes

    USGS Publications Warehouse

    Carl, Leon M.; McGuiness, Fiona

    2006-01-01

    This study compares simple fish communities of ten oligotrophic lakes in south-central Ontario. Species densities and population size structure vary significantly among these lake communities depending on fish species present beyond the littoral zone. Lake whitefish are fewer and larger in the presence of lake herring than in their absence. Diet analysis indicates that lake whitefish shift from feeding on both plankton and benthic prey when lake herring are absent to a primarily benthic feeding niche in the presence of lake herring. When benthic round whitefish are present, lake whitefish size and density decline and they move lower in the lake compared to round whitefish. Burbot are also fewer and larger in lakes with lake herring than in lakes without herring. Burbot, in turn, appear to influence the population structure of benthic coregonine species. Lower densities of benthic lake whitefish and round whitefish are found in lakes containing large benthic burbot than in lakes with either small burbot or where burbot are absent. Predation on the pelagic larvae of burbot and lake whitefish by planktivorous lake herring alters the size and age structure of these populations. As life history theory predicts, those species with poor larval survival appear to adopt a bet-hedging life history strategy of long-lived individuals as a reproductive reserve.

  4. Wrinkle Ridges and Young Fresh Crater

    NASA Image and Video Library

    2002-06-04

    This NASA Mars Odyssey image is of the ridged plains of Lunae Planum in the northern hemisphere of Mars. Wrinkle ridges, a very common landform on Mars, Mercury, Venus, and the Moon, are found mostly along the eastern side of the image.

  5. Observations of sea ice ridging in the Weddell Sea

    NASA Astrophysics Data System (ADS)

    Granberg, Hardy B.; Leppaäranta, Matti

    1999-11-01

    Sea ice surface topography data were obtained by helicopter-borne laser profiling during the First Finnish Antarctic Expedition (FINNARP-89). The measurements were made near the ice margin at about 73°S, 27°W in the eastern Weddell Sea on December 31, 1989, and January 1, 1990. Five transects, ranging in length from 127 to 163 km and covering a total length of 724 km, are analyzed. With a lower cutoff of 0.91 m the overall ridge frequency was 8.4 ridges/km and the average ridge height was 1.32 m. The spatial variations in ridging were large; for 36 individual 20-km segments the frequencies were 2-16 ridges/km and the mean heights were 1.16-1.56 m. The frequencies and mean heights were weakly correlated. The distributions of the ridge heights followed the exponential distribution; the spacings did not pass tests for either the exponential or the lognormal distribution, but the latter was much closer. In the 20-km segments the areally averaged thickness of ridged ice was 0.51±0.28 m, ranging from 0.10 to 1.15 m. The observed ridge size and frequency are greater than those known for the Ross Sea. Compared with the central Arctic, the Weddell Sea ridging frequencies are similar but the ridge heights are smaller, possibly as a result of differences in snow accumulation.

  6. Effects of recharge, Upper Floridan aquifer heads, and time scale on simulated ground-water exchange with Lake Starr, a seepage lake in central Florida

    USGS Publications Warehouse

    Swancar, Amy; Lee, Terrie Mackin

    2003-01-01

    Lake Starr and other lakes in the mantled karst terrain of Florida's Central Lake District are surrounded by a conductive surficial aquifer system that receives highly variable recharge from rainfall. In addition, downward leakage from these lakes varies as heads in the underlying Upper Floridan aquifer change seasonally and with pumpage. A saturated three-dimensional finite-difference ground-water flow model was used to simulate the effects of recharge, Upper Floridan aquifer heads, and model time scale on ground-water exchange with Lake Starr. The lake was simulated as an active part of the model using high hydraulic conductivity cells. Simulated ground-water flow was compared to net ground-water flow estimated from a rigorously derived water budget for the 2-year period August 1996-July 1998. Calibrating saturated ground-water flow models with monthly stress periods to a monthly lake water budget will result in underpredicting gross inflow to, and leakage from, ridge lakes in Florida. Underprediction of ground-water inflow occurs because recharge stresses and ground-water flow responses during rainy periods are averaged over too long a time period using monthly stress periods. When inflow is underestimated during calibration, leakage also is underestimated because inflow and leakage are correlated if lake stage is maintained over the long term. Underpredicted leakage reduces the implied effect of ground-water withdrawals from the Upper Floridan aquifer on the lake. Calibrating the weekly simulation required accounting for transient responses in the water table near the lake that generated the greater range of net ground-water flow values seen in the weekly water budget. Calibrating to the weekly lake water budget also required increasing the value of annual recharge in the nearshore region well above the initial estimate of 35 percent of the rainfall, and increasing the hydraulic conductivity of the deposits around and beneath the lake. To simulate the total

  7. Long Valley Caldera Lake and reincision of Owens River Gorge

    USGS Publications Warehouse

    Hildreth, Wes; Fierstein, Judy

    2016-12-16

    Owens River Gorge, today rimmed exclusively in 767-ka Bishop Tuff, was first cut during the Neogene through a ridge of Triassic granodiorite to a depth as great as its present-day floor and was then filled to its rim by a small basaltic shield at 3.3 Ma. The gorge-filling basalt, 200 m thick, blocked a 5-km-long reach of the upper gorge, diverting the Owens River southward around the shield into Rock Creek where another 200-m-deep gorge was cut through the same basement ridge. Much later, during Marine Isotope Stage (MIS) 22 (~900–866 ka), a piedmont glacier buried the diversion and deposited a thick sheet of Sherwin Till atop the basalt on both sides of the original gorge, showing that the basalt-filled reach had not, by then, been reexcavated. At 767 ka, eruption of the Bishop Tuff blanketed the landscape with welded ignimbrite, deeply covering the till, basalt, and granodiorite and completely filling all additional reaches of both Rock Creek canyon and Owens River Gorge. The ignimbrite rests directly on the basalt and till along the walls of Owens Gorge, but nowhere was it inset against either, showing that the basalt-blocked reach had still not been reexcavated. Subsidence of Long Valley Caldera at 767 ka produced a steep-walled depression at least 700 m deeper than the precaldera floor of Owens Gorge, which was beheaded at the caldera’s southeast rim. Caldera collapse reoriented proximal drainages that had formerly joined east-flowing Owens River, abruptly reversing flow westward into the caldera. It took 600,000 years of sedimentation in the 26-km-long, usually shallow, caldera lake to fill the deep basin and raise lake level to its threshold for overflow. Not until then did reestablishment of Owens River Gorge begin, by incision of the gorge-filling ignimbrite.

  8. Improved Digitization of Lunar Mare Ridges with LROC Derived Products

    NASA Astrophysics Data System (ADS)

    Crowell, J. M.; Robinson, M. S.; Watters, T. R.; Bowman-Cisneros, E.; Enns, A. C.; Lawrence, S.

    2011-12-01

    Lunar wrinkle ridges (mare ridges) are positive-relief structures formed from compressional stress in basin-filling flood basalt deposits [1]. Previous workers have measured wrinkle ridge orientations and lengths to investigate their spatial distribution and infer basin-localized stress fields [2,3]. Although these plots include the most prominent mare ridges and their general trends, they may not have fully captured all of the ridges, particularly the smaller-scale ridges. Using Lunar Reconnaissance Orbiter Wide Angle Camera (WAC) global mosaics and derived topography (100m pixel scale) [4], we systematically remapped wrinkle ridges in Mare Serenitatis. By comparing two WAC mosaics with different lighting geometry, and shaded relief maps made from a WAC digital elevation model (DEM) [5], we observed that some ridge segments and some smaller ridges are not visible in previous structure maps [2,3]. In the past, mapping efforts were limited by a fixed Sun direction [6,7]. For systematic mapping we created three shaded relief maps from the WAC DEM with solar azimuth angles of 0°, 45°, and 90°, and a fourth map was created by combining the three shaded reliefs into one, using a simple averaging scheme. Along with the original WAC mosaic and the WAC DEM, these four datasets were imported into ArcGIS, and the mare ridges of Imbrium, Serenitatis, and Tranquillitatis were digitized from each of the six maps. Since the mare ridges are often divided into many ridge segments [8], each major component was digitized separately, as opposed to the ridge as a whole. This strategy enhanced our ability to analyze the lengths, orientations, and abundances of these ridges. After the initial mapping was completed, the six products were viewed together to identify and resolve discrepancies in order to produce a final wrinkle ridge map. Comparing this new mare ridge map with past lunar tectonic maps, we found that many mare ridges were not recorded in the previous works. It was noted

  9. Europa Ridges, Hills and Domes

    NASA Technical Reports Server (NTRS)

    1997-01-01

    This moderate-resolution view of the surface of one of Jupiter's moons, Europa, shows the complex icy crust that has been extensively modified by fracturing and the formation of ridges. The ridge systems superficially resemble highway networks with overpasses, interchanges and junctions. From the relative position of the overlaps, it is possible to determine the age sequence for the ridge sets. For example, while the 8-kilometer-wide (5-mile) ridge set in the lower left corner is younger than most of the terrain seen in this picture, a narrow band cuts across the set toward the bottom of the picture, indicating that the band formed later. In turn, this band is cut by the narrow 2- kilometer-wide (1.2-mile) double ridge running from the lower right to upper left corner of the picture. Also visible are numerous clusters of hills and low domes as large as 9 kilometers (5.5 miles) across, many with associated dark patches of non-ice material. The ridges, hills and domes are considered to be ice-rich material derived from the subsurface. These are some of the youngest features seen on the surface of Europa and could represent geologically young eruptions.

    This area covers about 140 kilometers by 130 kilometers (87 miles by 81 miles) and is centered at 12.3 degrees north latitude, 268 degrees west longitude. Illumination is from the east (right side of picture). The resolution is about 180 meters (200 yards) per pixel, meaning that the smallest feature visible is about a city block in size. The picture was taken by the Solid State Imaging system on board the Galileo spacecraft on February 20, 1997, from a distance of 17,700 kilometers (11,000 miles) during its sixth orbit around Jupiter.

    The Jet Propulsion Laboratory, Pasadena, CA, manages the mission for NASA's Office of Space Science, Washington D.C. This image and other images and data received from Galileo are posted on the World Wide Web Galileo mission home page at http://galileo.jpl.nasa.gov.

  10. Ridge and Talus in Lycus Sulci

    NASA Image and Video Library

    2015-08-12

    This image from NASA Mars Reconnaissance Orbiter spacecraft nicely captures several influential geologic processes that have shaped the landscape of Lycus Sulci. Our observation covers an area of about 7.5 by 5.4 kilometers in Lycus Sulci, located just to the northwest of Olympus Mons in the Tharsis region of Mars. "Sulci" is a Latin term meaning "furrow" or "groove." In this case, Lycus Sulci is a region comprised of a series of depressions and ridges. Like most of the Tharsis region, Lycus Sulci exhibits thick deposits of light-toned Martian dust; the slopes on ridges in this region feature abundant streaks. These streaks are long, thin dark-toned features. They appear when the superficial light-tone fine-grained materials (i.e., Martian dust) suddenly move down slope and expose the darker underlying volcanic surfaces. Repeat imaging shows that dust streaks are consistently dark when they are initially formed and become lighter over time. This is due to the steady deposition of dust from the atmosphere. Slope streaks are also visible along the slopes of ridges and shallow depressions. Two ridges here exhibit partially exposed bedrock. These outcrops are interpreted to still have abundant coatings and dust, obscuring the underlying bedrock. This interpretation is based on the lack of bluish color for volcanic bedrock from the infrared-red-blue swath of our camera, and consistent with the homogenous tannish color we see throughout the same swath. It's possible that the ridges here and throughout the Lycus Sulci region formed via volcanic and tectonic processes, which have been further sculpted by wind erosion and other mass wasting processes. For example, talus slopes, which appear as fine-grained fans or conical-shaped deposits, originate from the steepest portions of the ridges. These form when the rocks or deposits on the steepest slopes of a ridge fail under the influence of Martian gravity and their own mass, causing an avalanche of these materials, which then

  11. Geology along the Blue Ridge Parkway in Virginia

    USGS Publications Warehouse

    Carter, Mark W.; Southworth, C. Scott; Tollo, Richard P.; Merschat, Arthur J.; Wagner, Sara; Lazor, Ava; Aleinikoff, John N.

    2017-01-01

    Detailed geologic mapping and new SHRIMP (sensitive high-resolution ion microprobe) U-Pb zircon, Ar/Ar, Lu-Hf, 14C, luminescence (optically stimulated), thermochronology (fission-track), and palynology reveal the complex Mesoproterozoic to Quaternary geology along the ~350 km length of the Blue Ridge Parkway in Virginia. Traversing the boundary of the central and southern Appalachians, rocks along the parkway showcase the transition from the para-autochthonous Blue Ridge anticlinorium of northern and central Virginia to the allochthonous eastern Blue Ridge in southern Virginia. From mile post (MP) 0 near Waynesboro, Virginia, to ~MP 124 at Roanoke, the parkway crosses the unconformable to faulted boundary between Mesoproterozoic basement in the core of the Blue Ridge anticlinorium and Neoproterozoic to Cambrian metasedimentary and metavolcanic cover rocks on the western limb of the structure. Mesoproterozoic basement rocks comprise two groups based on SHRIMP U-Pb zircon geochronology: Group I rocks (1.2-1.14 Ga) are strongly foliated orthogneisses, and Group II rocks (1.08-1.00 Ga) are granitoids that mostly lack obvious Mesoproterozoic deformational features.Neoproterozoic to Cambrian cover rocks on the west limb of the anticlinorium include the Swift Run and Catoctin Formations, and constituent formations of the Chilhowee Group. These rocks unconformably overlie basement, or abut basement along steep reverse faults. Rocks of the Chilhowee Group are juxtaposed against Cambrian rocks of the Valley and Ridge province along southeast- and northwest-dipping, high-angle reverse faults. South of the James River (MP 64), Chilhowee Group and basement rocks occupy the hanging wall of the nearly flat-lying Blue Ridge thrust fault and associated splays.South of the Red Valley high-strain zone (MP 144.5), the parkway crosses into the wholly allochthonous eastern Blue Ridge, comprising metasedimentary and meta-igneous rocks assigned to the Wills Ridge, Ashe, and Alligator

  12. Lithospheric Flexural Modeling of Iapetus' Equatorial Ridge

    NASA Astrophysics Data System (ADS)

    Zheng, W.; Ip, W.-H.; Teng, L. S.

    2012-04-01

    Iapetus, which is one of Saturn's ball-shaped satellites, has some unique features in the Solar System. This satellite has a mean radius of 735 km, and there is an approximately 20-kilometer-high mountain lying precisely on its equator. The mountain is known as an "equatorial ridge" since it makes Iapetus appear walnut shaped. The origin of the equatorial ridge is attributed to several hypotheses, including different endogenesis and exogenesis processes. In this work, we attempted to construct a flexural model of the equatorial ridge using elastic lithosphere theory. The equatorial ridge is treated as a linear load which exerts uniform force on Iapetus' hard shell (i.e. elastic lithosphere of Iapetus). To calculate the deflection of surface, we use the Digital Terrain Model (DTM) data of Iapetus' leading side published by Giese et al. (2008). Giese et al. also pointed out that the elastic lithospheric thickness of Iapetus must exceed 100 km to support the ridge without deflecting. However, we found possible evidence in the DTM data that implied deflection. There are two sites of surface depression on the northern side of the equatorial ridge. The few-kilometer deflection implies a thinner lithosphere than previous suggested. Assume that the thickness of elastic lithosphere is only 5% below of the radius of Iapetus, so the flat-Earth and one-plate condition could adapt to the flexure model of Iapetus. Based on analysis of the distance between a bulge and the ridge, the calculated lithospheric thickness is 6-10 km. The new result seems controversial, but the modeled surface profile is highly consistent with numerical ridge DTM profile extracted from Giese et al. (2008). Thinner lithosphere also supports the contraction model proposed by Sandwell and Schubert (2010) since the bucking harmonic degree increases. In the other hand, the transformation layer between hard shell and plastic inner core may need constraint on thermal history or crystal form of ice. In

  13. Characteristics of Hydrothermal Mineralization in Ultraslow Spreading Ridges

    NASA Astrophysics Data System (ADS)

    Zhou, H.; Yang, Q.; Ji, F.; Dick, H. J.

    2014-12-01

    Hydrothermal activity is a major component of the processes that shape the composition and structure of the ocean crust, providing a major pathway for the exchange of heat and elements between the Earth's crust and oceans, and a locus for intense biological activity on the seafloor and underlying crust. In other hand, the structure and composition of hydrothermal systems are the result of complex interactions between heat sources, fluids, wall rocks, tectonic controls and even biological processes. Ultraslow spreading ridges, including the Southwest Indian Ridge, the Gakkel Ridge, are most remarkable end member in plate-boundary structures (Dick et al., 2003), featured with extensive tectonic amagmatic spreading and frequent exposure of peridotite and gabbro. With intensive surveys in last decades, it is suggested that ultraslow ridges are several times more effective than faster-spreading ridges in sustaining hydrothermal activities. This increased efficiency could attributed to deep mining of heat and even exothermic serpentinisation (Baker et al., 2004). Distinct from in faster spreading ridges, one characteristics of hydrothermal mineralization on seafloor in ultraslow spreading ridges, including the active Dragon Flag hydrothermal field at 49.6 degree of the Southwest Indian Ridge, is abundant and pervasive distribution of lower temperature precipitated minerals ( such as Fe-silica or silica, Mn (Fe) oxides, sepiolite, pyrite, marcasite etc. ) in hydrothermal fields. Structures formed by lower temperature activities in active and dead hydrothermal fields are also obviously. High temperature precipitated minerals such as chalcopyrite etc. are rare or very limited in hydrothermal chimneys. Distribution of diverse low temperature hydrothermal activities is consistence with the deep heating mechanisms and hydrothermal circulations in the complex background of ultraslow spreading tectonics. Meanwhile, deeper and larger mineralization at certain locations along the

  14. Glacial modulation of mid-ocean ridge magmatism and anomalous Pacific Antarctic Ridge volcanism during Termination II

    NASA Astrophysics Data System (ADS)

    Asimow, P. D.; Lewis, M.; Lund, D. C.; Seeley, E.; McCart, S.; Mudahy, A.

    2017-12-01

    Glacially-driven sea level rise and fall may modulate submarine volcanism by superposing pressure changes on the tectonic decompression that causes melt production in the mantle below mid-ocean ridges. A number of recent studies have considered whether this effect is recorded in the periodicity of ridge flank bathymetry (Tolstoy, 2015; Crowley et al., 2015) but interpretation of the bathymetric data remains controversial (Goff, 2016; Olive et al., 2016). We have pursued an independent approach using hydrothermal metals in well-dated near-ridge sediment cores. Along the full length of the East Pacific Rise, in areas of the ocean with widely variable biologic productivity, there are large and consistent rises in Fe, Mn, and As concentrations during the last two glacial terminations. We interpret these cores as records of excess hydrothermal flux due to delayed delivery to the axis of excess melt generated by the preceding falls in sea level. Here we discuss the potentially related discovery, in a core near the Pacific Antarctic Ridge (PAR), of a 10 cm thick layer of basaltic ash shards up to 250 mm in size, coincident with the penultimate deglaciation (Termination II). Although the site was 8 km off-axis at the time, the glasses have major element, volatile, and trace element composition consistent with more evolved members of the axial MORB suite from the nearby ridge axis. Their morphologies are typical of pyroclastic deposits created by explosive submarine volcanism (Clague et al., 2009). We propose that a period of low magmatic flux following a sea-level rise caused cooling of crustal magmatic systems, more advanced fractionation in the axial magma chamber, and increases in viscosity and volatile concentration. We hypothesize subsequent arrival of high magmatic flux during Termination II then reactivated the system and triggered an unusually vigorous series of explosive eruptions along this segment of the PAR. Ash layers recording large eruptions such as this one

  15. Ridge Orientations of the Ridge-Forming Unit, Sinus Meridiani, Mars-A Fluvial Explanation

    NASA Technical Reports Server (NTRS)

    Wilkinson, M. Justin; Herridge, A.

    2013-01-01

    Imagery and MOLA data were used in an analysis of the ridge-forming rock unit (RFU) exposed in Sinus Meridiani (SM). This unit shows parallels at different scales with fluvial sedimentary bodies. We propose the terrestrial megafan as the prime analog for the RFU, and likely for other members of the layered units. Megafans are partial cones of fluvial sediment, with radii up to hundreds of km. Although recent reviews of hypotheses for the RFU units exclude fluvial hypotheses [1], inverted ridges in the deserts of Oman have been suggested as putative analogs for some ridges [2], apparently without appreciating The wider context in which these ridges have formed is a series of megafans [3], a relatively unappreciated geomorphic feature. It has been argued that these units conform to the megafan model at the regional, subregional and local scales [4]. At the regional scale suites of terrestrial megafans are known to cover large areas at the foot of uplands on all continents - a close parallel with the setting of the Meridiani sediments at the foot of the southern uplands of Mars, with its incised fluvial systems leading down the regional NW slope [2, 3] towards the sedimentary units. At the subregional scale the layering and internal discontinuities of the Meridiani rocks are consistent, inter alia, with stacked fluvial units [4]. Although poorly recognized as such, the prime geomorphic environment in which stream channel networks cover large areas, without intervening hillslopes, is the megafan [see e.g. 4]. Single megafans can reach 200,000 km2 [5]. Megafans thus supply an analog for areas where channel-like ridges (as a palimpsest of a prior landscape) cover the intercrater plains of Meridiani [6]. At the local, or river-reach scale, the numerous sinuous features of the RFU are suggestive of fluvial channels. Cross-cutting relationships, a common feature of channels on terrestrial megafans, are ubiquitous. Desert megafans show cemented paleo-channels as inverted

  16. New data of the Gakkel Ridge seismicity

    NASA Astrophysics Data System (ADS)

    Antonovskaya, Galina; Basakina, Irina; Kremenetskaya, Elena

    2016-04-01

    250 earthquakes were recorded in the Gakkel Ridge during the period 2012-2014 by Arkhangelsk seismic network. The magnitude Ml of these earthquakes is 1.5 - 5.7, 70% of them have Ml up to 3.0. Seismic events are arranged along to a narrow center line of the Mid-Arctic Ridge, most of the earthquakes are confined to the southern board of the Ridge. Presumably it's connected with the reflection of spreading processes. The high seismic activity zones, which we associate with the volcano-tectonic processes, have been identified. Have been recorded 13 events per day in the Western Volcanic Zone. The largest number of events (75%) is confined to the Sparsely Magmatic Zone. About 30% of all recorded earthquakes with magnitudes above 2.9 have a T-phase. We divided the Gakkel Ridge's earthquakes into two groups by using spectral-time analysis. The first group: maximum energy of the earthquake is observed from 1.5 to 10 Hz, values of magnitudes Ml 2.50-5.29. Earthquakes are distributed along the Gakkel Ridge. The second group: maximum energy of the earthquake is observed from 1.5 to 20 Hz, clearly expressed a high-frequency component, values of magnitudes Ml 2.3-3.4. Earthquakes 2 groups focused only in the Sparsely Magmatic Zone. The new seismic data shows an unique information about geodynamic processes of the Gakkel Ridge.

  17. Field sampling and analysis plan for the remedial investigation of Waste Area Grouping 2 at Oak Ridge National Laboratory, Oak Ridge, Tennessee. Environmental Restoration Program

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Boston, H.L.; Ashwood, T.L.; Borders, D.M.

    1992-02-01

    This field sampling and analysis (S & A) plan has been developed as part of the Department of Energy`s (DOE`s) remedial investigation (RI) of Waste Area Grouping (WAG) 2 at Oak Ridge National Laboratory (ORNL) located in Oak Ridge, Tennessee. The S & A plan has been written in support of the remedial investigation (RI) plan for WAG 2 (ORNL 1990). WAG 2 consists of White Oak Creek (WOC) and its tributaries downstream of the ORNL main plant area, White Oak Lake (WOL), White Oak Creek embayment (WOCE) on the Clinch River, and the associated floodplain and subsurface environment (Fig.more » 1.1). The WOC system is the surface drainage for the major ORNL WAGs and has been exposed to a diversity of contaminants from operations and waste disposal activities in the WOC watershed. WAG 2 acts as a conduit through which hydrologic fluxes carry contaminants from upgradient areas to the Clinch River. Water, sediment, soil, and biota in WAG 2 are contaminated and continue to receive contaminants from upgradient WAGs. This document describes the following: an overview of the RI plan, background information for the WAG 2 system, and objectives of the S & A plan; the scope and implementation of the first 2 years of effort of the S & A plan and includes recent information about contaminants of concern, organization of S & A activities, interactions with other programs, and quality assurance specific to the S & A activities; provides details of the field sampling plans for sediment, surface water, groundwater, and biota, respectively; and describes the sample tracking and records management plan.« less

  18. Morphology, volcanism, and mass wasting in Crater Lake, Oregon

    USGS Publications Warehouse

    Bacon, C.R.; Gardner, J.V.; Mayer, L.A.; Buktenica, M.W.; Dartnell, P.; Ramsey, D.W.; Robinson, J.E.

    2002-01-01

    Crater Lake was surveyed nearly to its shoreline by high-resolution multibeam echo sounding in order to define its geologic history and provide an accurate base map for research and monitoring surveys. The bathymetry and acoustic backscatter reveal the character of landforms and lead to a chronology for the concurrent filling of the lake and volcanism within the ca. 7700 calibrated yr B.P. caldera. The andesitic Wizard Island and central-plattform volcanoes are composed of sequences of lava deltas that record former lake levels and demonstrate simultaneous activity at the two vents. Wizard Island eruptions ceased when the lake was ~80 m lower than at present. Lava streams from prominent channels on the surface of the central platform descended to feed extensive subaqueous flow fields on the caldera floor. The Wizard Island and central-platform volcanoes, andesitic Merriam Cone, and a newly discovered probable lava flow on the eastern floor of the lake apparently date from within a few hundred years of caldera collapse, whereas a small rhydacite dome was emplaced on the flank of Wizard Island at ca. 4800 cal. yr B.P. Bedrock outcrops on the submerged caldera walls are shown in detail and, in some cases, can be correlated with exposed geologic units of Mount Mazama. Fragmental debris making up the walls elsewhere consists of narrow talus cones forming a dendritic pattern that leads to fewer, wider ridges downslope. Hummocky topography and scattered blocks up to ~280 m long below many of the embayments in the caldera wall mark debris-avalanche deposits that probably formed in single events and commonly are affected by secondary failures. The flat-floored, deep basins contain relatively fine-grained sediment transported from the debris aprons by sheet-flow turbidity currents. Crater Lake apparently filled rapidly (ca. 400-750 yr) until reaching a permeable layer above glaciated lava identified by the new survey in the northeast caldera wall at ~1845 m elevation

  19. High-Resolution Image of Europa's Ridged Plains

    NASA Technical Reports Server (NTRS)

    1998-01-01

    This spectacular image taken by NASA's Galileo spacecraft camera shows a region of ridged plains on Jupiter's moon Europa. The plains are comprised of many parallel and cross-cutting ridges, commonly in pairs. The majority of the region is of very bright, but darker material is seen primarily in valleys between ridges. Some of the most prominent ridges have dark deposits along their margins and in their central valleys. Some of this dark material probably moved down the flanks of the ridges and has piled up along their bases. The most prominent ridges are about a kilometer in width (less than a mile). In the top right hand corner of the image the end of a dark wide ridge (about 2 kilometers or 1.2 miles across) is visible. Several deep fractures cut through this ridge and continue into the plains. The brightness of the region suggests that frost covers much of Europa's surface. This image looks different from those obtained earlier in Galileo's mission, because this image was taken with the Sun higher in Europa's sky.

    This image was taken on December 16, 1997 at a range of 1,300 kilometers (800 miles) by Galileo's solid state imaging system. North is to the top of the picture, and the Sun illuminates the surface from the upper left. This image, centered at approximately 14 degrees south latitude and 194 degrees west longitude, covers an area approximately 20 kilometers (12 miles) on each side. The resolution is 26 meters (85 feet) per picture element.

    The Jet Propulsion Laboratory, Pasadena, CA manages the Galileo mission for NASA's Office of Space Science, Washington, DC. JPL is an operating division of California Institute of Technology (Caltech).

    This image and other images and data received from Galileo are posted on the World Wide Web, on the Galileo mission home page at URL http://www.jpl.nasa.gov/ galileo.

  20. 2016 Lake Michigan Lake Trout Working Group Report

    USGS Publications Warehouse

    Madenjian, Charles P.; Breidert, Brian; Boyarski, David; Bronte, Charles R.; Dickinson, Ben; Donner, Kevin; Ebener, Mark P.; Gordon, Roger; Hanson, Dale; Holey, Mark; Janssen, John; Jonas, Jory; Kornis, Matthew; Olsen, Erik; Robillard, Steve; Treska, Ted; Weldon, Barry; Wright, Greg D.

    2017-01-01

    This report provides a review on the progression of lake trout rehabilitation towards meeting the Salmonine Fish Community Objectives (FCOs) for Lake Michigan (Eshenroder et. al. 1995) and the interim goal and evaluation objectives articulated in A Fisheries Management Implementation Strategy for the Rehabilitation of Lake Trout in Lake Michigan (Dexter et al. 2011); we also include data describing lake trout stocking and mortality to portray the present state of progress towards lake trout rehabilitation.

  1. Contaminants in American alligator eggs from Lake Apopka, Lake Griffin, and Lake Okeechobee, Florida

    USGS Publications Warehouse

    Heinz, Gary H.; Percival, H. Franklin; Jennings, Michael L.

    1991-01-01

    Residues of organochlorine pesticides, polychlorinated biphenyls (PCBs), and 16 elements were measured in American alligator (Alligator mississippiensis) eggs collected in 1984 from Lakes Apopka, Griffin, and Okeechobee in central and south Florida. Organochlorine pesticides were highest in eggs from Lake Apopka. None of the elements appeared to be present at harmful concentrations in eggs from any of the lakes. A larger sample of eggs was collected in 1985, but only from Lakes Griffin, a lake where eggs were relatively clean, and Apopka, where eggs were most contaminated. In 1985, hatching success of artificially incubated eggs was lower for Lake Apopka, and several organochlorine pesticides were higher than in eggs from Lake Griffin. However, within Lake Apopka, higher levels of pesticides in chemically analyzed eggs were not associated with reduced hatching success of the remaining eggs in the clutch. Therefore, it did not appear that any of the pesticides we measured were responsible for the reduced hatching success of Lake Apopka eggs.

  2. ENVIRONMENTAL BASELINE SURVEY REPORT FOR WEST BLACK OAK RIDGE, EAST BLACK OAK RIDGE, MCKINNEY RIDGE, WEST PINE RIDGE, AND PARCEL 21D IN THE VICINITY OF THE EAST TENNESSEE TECHNOLOGY PARK, OAK RIDGE, TENNESSEE

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    David A. King

    2012-11-29

    This environmental baseline survey (EBS) report documents the baseline environmental conditions of five land parcels located near the U.S. Department of Energy’s (DOE’s) East Tennessee Technology Park (ETTP), including West Black Oak Ridge, East Black Oak Ridge, McKinney Ridge, West Pine Ridge, and Parcel 21d. The goal is to obtain all media no-further-investigation (NFI) determinations for the subject parcels considering existing soils. To augment the existing soils-only NFI determinations, samples of groundwater, surface water, soil, and sediment were collected to support all media NFI decisions. The only updates presented here are those that were made after the original issuance ofmore » the NFI documents. In the subject parcel where the soils NFI determination was not completed for approval (Parcel 21d), the full process has been performed to address the soils as well. Preparation of this report included the detailed search of federal government records, title documents, aerial photos that may reflect prior uses, and visual inspections of the property and adjacent properties. Interviews with current employees involved in, or familiar with, operations on the real property were also conducted to identify any areas on the property where hazardous substances and petroleum products, or their derivatives, and acutely hazardous wastes may have been released or disposed. In addition, a search was made of reasonably obtainable federal, state, and local government records of each adjacent facility where there has been a release of any hazardous substance or any petroleum product or their derivatives, including aviation fuel and motor oil, and which is likely to cause or contribute to a release of any hazardous substance or any petroleum product or its derivatives, including aviation fuel or motor oil, on the real property. A radiological survey and soil/sediment sampling was conducted to assess baseline conditions of Parcel 21d that were not addressed by the soils

  3. Sanctuaries for lake trout in the Great Lakes

    USGS Publications Warehouse

    Stanley, Jon G.; Eshenroder, Randy L.; Hartman, Wilbur L.

    1987-01-01

    Populations of lake trout, severely depleted in Lake Superior and virtually extirpated from the other Great Lakes because of sea lamprey predation and intense fishing, are now maintained by annual plantings of hatchery-reared fish in Lakes Michigan, Huron, and Ontario and parts of Lake Superior. The extensive coastal areas of the Great Lakes and proximity to large populations resulted in fishing pressure on planted lake trout heavy enough to push annual mortality associated with sport and commercial fisheries well above the critical level needed to reestablish self-sustaining stocks. The interagency, international program for rehabilitating lake trout includes controlling sea lamprey abundance, stocking hatchery-reared lake trout, managing the catch, and establishing sanctuaries where harvest is prohibited. Three lake trout sanctuaries have been established in Lake Michigan: the Fox Island Sanctuary of 121, 500 ha, in the Chippewa-Ottawa Treaty fishing zone in the northern region of the lake; the Milwaukee Reef Sanctuary of 160, 000 ha in midlake, in boundary waters of Michigan and Wisconsin; and Julian's Reef Sanctuary of 6, 500 ha, in Illinois waters. In northern Lake Huron, Drummond Island Sanctuary of 55, 000 ha is two thirds in Indian treaty-ceded waters in Michigan and one third in Ontario waters of Canada. A second sanctuary, Six Fathom Bank-Yankee Reef Sanctuary, in central Lake Huron contains 168, 000 ha. Sanctuary status for the Canadian areas remains to be approved by the Provincial government. In Lake Superior, sanctuaries protect the spawning grounds of Gull Island Shoal (70, 000 ha) and Devils Island Shoal (44, 000 ha) in Wisconsin's Apostle Island area. These seven sanctuaries, established by the several States and agreed upon by the States, Indian tribes, the U.S. Department of the Interior, and the Province of Ontario, contribute toward solving an interjurisdictional fishery problem.

  4. Late Quaternary tectonic activity and lake level change in the Rukwa Rift Basin

    NASA Astrophysics Data System (ADS)

    Delvaux, D.; Kervyn, F.; Vittori, E.; Kajara, R. S. A.; Kilembe, E.

    1998-04-01

    Interpretation of remotely sensed images and air photographs, compilation of geological and topographical maps, morphostructural and fault kinematic observations and 14C dating reveal that, besides obvious climatic influences, the lake water extent and sedimentation in the closed hydrological system of Lake Rukwa is strongly influenced by tectonic processes. A series of sandy ridges, palaeolacustrine terraces and palaeounderwater delta fans are related to an Early Holocene high lake level and subsequent progressive lowering. The maximum lake level was controlled by the altitude of the watershed between the Rukwa and Tanganyika hydrological systems. Taking as reference the present elevation of the palaeolacustrine terraces around Lake Rukwa, two orders of vertical tectonic movement are evidenced: i) a general uplift centred on the Rungwe Volcanic Province between the Rukwa and Malawi Rift Basins; and ii) a tectonic northeastward tilting of the entire Rukwa Rift Basin, including the depression and rift shoulders. This is supported by the observed hydromorphological evolution. Local uplift is also induced by the development of an active fault zone in the central part of the depression, in a prolongation of the Mbeya Range-Galula Fault system. The Ufipa and Lupa Border Faults, bounding the Rukwa depression on the southwestern and northeastern sides, respectively, exert passive sedimentation control only. They appear inactive or at least less active in the Late Quaternary than during the previous rifting stage. The main Late Quaternary tectonic activity is represented by dextral strike-slip movement along the Mbeya Range-Galula Fault system, in the middle of the Rukwa Rift Basin, and by normal dip-slip movements along the Kanda Fault, in the western rift shoulder.

  5. Rhelogical constraints on ridge formation on Icy Satellites

    NASA Astrophysics Data System (ADS)

    Rudolph, M. L.; Manga, M.

    2010-12-01

    The processes responsible for forming ridges on Europa remain poorly understood. We use a continuum damage mechanics approach to model ridge formation. The main objectives of this contribution are to constrain (1) choice of rheological parameters and (2) maximum ridge size and rate of formation. The key rheological parameters to constrain appear in the evolution equation for a damage variable (D): ˙ {D} = B <<σ >>r}(1-D){-k-α D (p)/(μ ) and in the equation relating damage accumulation to volumetric changes, Jρ 0 = δ (1-D). Similar damage evolution laws have been applied to terrestrial glaciers and to the analysis of rock mechanics experiments. However, it is reasonable to expect that, like viscosity, the rheological constants B, α , and δ depend strongly on temperature, composition, and ice grain size. In order to determine whether the damage model is appropriate for Europa’s ridges, we must find values of the unknown damage parameters that reproduce ridge topography. We perform a suite of numerical experiments to identify the region of parameter space conducive to ridge production and show the sensitivity to changes in each unknown parameter.

  6. Water quality of Lake Austin and Town Lake, Austin, Texas

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Andrews, F.L.; Wells, F.C.; Shelby, W.J.

    1988-01-01

    Lake Austin and Town Lake are impoundments on the Colorado River in Travis County, central Texas, and are a source of water for municipal industrial water supplies, electrical-power generation, and recreation for more than 500,000 people in the Austin metropolitan area. Small vertical temperature variations in both lakes were attributed to shallow depths in the lakes and short retention times of water in the lakes during the summer months. The largest areal variations in dissolved oxygen generally occur in Lake Austin during the summer as a result of releases of water from below the thermocline in Lake Travis. Except formore » iron, manganese, and mercury, dissolved concentrations of trace elements in water collected from Lake Austin and Town Lake did not exceed the primary or secondary drinking water standards set by the US Environmental Protection Agency. Little or no effect of stormwater runoff on temperature, dissolved oxygen, or minor elements could be detected in either Lake Austin or Town Lake. Little seasonal or areal variation was noted in nitrogen concentrations in Lake Austin or Town lake. Total phosphorus concentrations generally were small in both lakes. Increased concentrations of nitrogen and phosphorus were detected after storm runoff inflow in Town Lake, but not in Lake Austin; densities of fecal-coliform bacteria increased in Lake Austin and Town Lake, but were substantially greater in Town Lake than in Lake Austin. 18 refs., 38 figs., 59 tabs.« less

  7. Dynamical Instability Produces Transform Faults at Mid-Ocean Ridges

    NASA Astrophysics Data System (ADS)

    Gerya, Taras

    2010-08-01

    Transform faults at mid-ocean ridges—one of the most striking, yet enigmatic features of terrestrial plate tectonics—are considered to be the inherited product of preexisting fault structures. Ridge offsets along these faults therefore should remain constant with time. Here, numerical models suggest that transform faults are actively developing and result from dynamical instability of constructive plate boundaries, irrespective of previous structure. Boundary instability from asymmetric plate growth can spontaneously start in alternate directions along successive ridge sections; the resultant curved ridges become transform faults within a few million years. Fracture-related rheological weakening stabilizes ridge-parallel detachment faults. Offsets along the transform faults change continuously with time by asymmetric plate growth and discontinuously by ridge jumps.

  8. The morphology of the ridge belts on Venus

    NASA Astrophysics Data System (ADS)

    Kriuchkov, V. P.

    1990-06-01

    The length and spacing of linear features were measured for ridge and groove belts, for the outer mountain zones of the Lakshmi planum, and for the outer ridge zones of coronal structures. The distributions of these parameters show small but significant differences in most of the cases. The ridges are assumed to result from deformations. Deformed-layer thickness were estimated for various types of linear subdivisions.

  9. A deep structural ridge beneath central India

    NASA Astrophysics Data System (ADS)

    Agrawal, P. K.; Thakur, N. K.; Negi, J. G.

    A joint-inversion of magnetic satellite (MAGSAT) and free air gravity data has been conducted to quantitatively investigate the cause for Bouguer gravity anomaly over Central Indian plateaus and possible fold consequences beside Himalayan zone in the Indian sub-continent due to collision between Indian and Eurasian plates. The appropriate inversion with 40 km crustal depth model has delineated after discriminating high density and magnetisation models, for the first time, about 1500 km long hidden ridge structure trending NW-SE. The structure is parallel to Himalayan fold axis and the Indian Ocean ridge in the Arabian Sea. A quantitative relief model across a representative anomaly profile confirms the ridge structure with its highest point nearly 6 km higher than the surrounding crustal level in peninsular India. The ridge structure finds visible support from the astro-geoidal contours.

  10. 27 CFR 9.158 - Mendocino Ridge.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 1 2010-04-01 2010-04-01 false Mendocino Ridge. 9.158 Section 9.158 Alcohol, Tobacco Products and Firearms ALCOHOL AND TOBACCO TAX AND TRADE BUREAU, DEPARTMENT OF THE TREASURY LIQUORS AMERICAN VITICULTURAL AREAS Approved American Viticultural Areas § 9.158 Mendocino Ridge. (a) Name. The name of the...

  11. 27 CFR 9.158 - Mendocino Ridge.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 1 2014-04-01 2014-04-01 false Mendocino Ridge. 9.158 Section 9.158 Alcohol, Tobacco Products and Firearms ALCOHOL AND TOBACCO TAX AND TRADE BUREAU, DEPARTMENT OF THE TREASURY ALCOHOL AMERICAN VITICULTURAL AREAS Approved American Viticultural Areas § 9.158 Mendocino Ridge. (a) Name. The name of the...

  12. 27 CFR 9.158 - Mendocino Ridge.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 1 2011-04-01 2011-04-01 false Mendocino Ridge. 9.158 Section 9.158 Alcohol, Tobacco Products and Firearms ALCOHOL AND TOBACCO TAX AND TRADE BUREAU, DEPARTMENT OF THE TREASURY LIQUORS AMERICAN VITICULTURAL AREAS Approved American Viticultural Areas § 9.158 Mendocino Ridge. (a) Name. The name of the...

  13. 27 CFR 9.158 - Mendocino Ridge.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 1 2013-04-01 2013-04-01 false Mendocino Ridge. 9.158 Section 9.158 Alcohol, Tobacco Products and Firearms ALCOHOL AND TOBACCO TAX AND TRADE BUREAU, DEPARTMENT OF THE TREASURY ALCOHOL AMERICAN VITICULTURAL AREAS Approved American Viticultural Areas § 9.158 Mendocino Ridge. (a) Name. The name of the...

  14. 27 CFR 9.158 - Mendocino Ridge.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 1 2012-04-01 2012-04-01 false Mendocino Ridge. 9.158 Section 9.158 Alcohol, Tobacco Products and Firearms ALCOHOL AND TOBACCO TAX AND TRADE BUREAU, DEPARTMENT OF THE TREASURY LIQUORS AMERICAN VITICULTURAL AREAS Approved American Viticultural Areas § 9.158 Mendocino Ridge. (a) Name. The name of the...

  15. Student Health Services at Orchard Ridge.

    ERIC Educational Resources Information Center

    Nichols, Don D.

    This paper provides a synoptic review of student health services at the community college level while giving a more detailed description of the nature of health services at Orchard Ridge, a campus of Oakland Community College. The present College Health Service program provides for a part-time (24 hrs./wk.) nurse at Orchard Ridge. A variety of…

  16. Alkalic Basalt in Ridge Axis of 53˚E Amagmatic Segment Center, Southwest Indian Ridge

    NASA Astrophysics Data System (ADS)

    Zhou, H.; Wang, J.; Liu, Y.; Ji, F.; Dick, H. J.

    2014-12-01

    Mid-ocean ridge basalt (MORB) is key tracer of composition and process in the mantle. It is interesting to notice that some alkalic basalts occur in amagmatic spreading center of ultraslow spreading ridges, for examples, 9-16˚E of the Southwest Indian ridge (Standish et al., 2008) and Lena Trough of Arctic Ocean (Snow et al., 2011). The latter is interpreted as the result of the pre-existence of continental transform fault or the especially cold thermal structure of ancient continental lithosphere. 53˚E segment, east of the Gallieni transform fault, was discovered as an amagmatic segment (Zhou and Dick, 2013). On both sides of the ridge axis, peridotites with a little gabbro are exposed in an area more than 3200 km2. Basalts exist in the southern portion of 53˚E segment, indicating the transformation from magmatic to amagmatic spreading about 9.4 million years ago. In April of 2014, Leg 4 of the RV Dayang Yihao cruise 30, basaltic glasses was dredged at one location (3500 m water depth) in the ridge axis of 53˚E segment center. It is shown by electric probe analysis that the samples have extremely high sodium content (4.0-4.49 wt% Na­2O ), relative higher potassium content (0.27-0.32 wt% K2O) and silica (50.67-51.87 wt% SiO2), and lower MgO content (5.9-6.4 wt% MgO). Mg-number is 0.55-0.59. It is distinctly different from the N-MORB (2.42-2.68 wt% Na2O, 0.03-0.06 wt% K2O, 48.6-49.6 wt% Si2O, 8.8-9.0 wt% MgO, Mg-numbers 0.63) distributed in the 560-km-long supersegment, west of the Gallieni transform fault, where the active Dragon Flag hydrothermal field was discovered at 49.6˚E in 2007. The reasons for the alkalic basalt in the ridge axis of 53˚E amagmatic segment center, either by low melting degree of garnet stability field, by melting from an ancient subcontinental lithospheric mantle, or by sodium-metasomatism or even other mantle processes or their combination in the deep mantle, are under further studies.

  17. Evidence of offshore lake trout reproduction in Lake Huron

    USGS Publications Warehouse

    DeSorcie, Timothy J.; Bowen, Charles A.

    2003-01-01

    Six Fathom Bank-Yankee Reef, an offshore reef complex, was an historically important spawning area believed to represent some of the best habitat for the rehabilitation of lake trout Salvelinus namaycush in Lake Huron. Since 1986, lake trout have been stocked on these offshore reefs to reestablish self-sustaining populations. We sampled with beam trawls to determine the abundance of naturally reproduced age-0 lake trout on these offshore reefs during May-July in 1994-1998 and 2000-2002. In total, 123 naturally reproduced lake trout fry were caught at Six Fathom Bank, and 2 naturally reproduced lake trout fry were caught at nearby Yankee Reef. Our findings suggest that this region of Lake Huron contains suitable habitat for lake trout spawning and offers hope that lake trout rehabilitation can be achieved in the main basin of Lake Huron.

  18. Proposed Great Salt Lake Basin Hydrologic Observatory

    NASA Astrophysics Data System (ADS)

    Johnson, W. P.; Tarboton, D. G.

    2004-12-01

    The dynamic physiography and population growth within the Great Salt Lake Basin provide the opportunity to observe climate and human-induced land-surface changes affecting water availability, water quality, and water use, thereby making the Great Salt Lake Basin a microcosm of contemporary water resource issues and an excellent site to pursue interdisciplinary and integrated hydrologic science. Important societal concerns center on: How do climate variability and human-induced landscape changes affect hydrologic processes, water quality and availability, and aquatic ecosystems over a range of scales? What are the resource, social, and economic consequences of these changes? The steep topography and large climatic gradients of the Great Salt Lake Basin yield hydrologic systems that are dominated by non-linear interactions between snow deposition and snow melt in the mountains, stream flow and groundwater recharge in the mid-elevations, and evaporative losses from the desert floor at lower elevations. Because the Great Salt Lake Basin terminates in a closed basin lake, it is uniquely suited to closing the water, solute, and sediment balances in a way that is rarely possible in a watershed of a size sufficient for coupling to investigations of atmospheric processes. Proposed infrastructure will include representative densely instrumented focus areas that will be nested within a basin-wide network, thereby quantifying fluxes, residence times, pathways, and storage volumes over a range of scales and land uses. The significant and rapid ongoing urbanization presents the opportunity for observations that quantify the interactions among hydrologic processes, human induced changes and social and economic dynamics. One proposed focus area will be a unique, highly instrumented mountain-to-basin transect that will quantify hydrologic processes extending from the mountain ridge top to the Great Salt Lake. The transect will range in elevation from about 1200 m to 3200 m, with a

  19. Lake Nasser and Toshka Lakes, Egypt

    NASA Technical Reports Server (NTRS)

    2002-01-01

    Lake Nasser (center) and the Toshka Lakes (center left) glow emerald green and black in this MODIS true-color image acquired March 8, 2002. Located on and near the border of Egypt and Norther Sudan, these lakes are an oasis of water in between the Nubian (lower right) and Libyan Deserts (upper left). Also visible are the Red Sea (in the upper right) and the Nile River (running north from Lake Nasser). Credit: Jacques Descloitres, MODIS Land Rapid Response Team, NASA/GSFC

  20. Ridge Waveguide Structures in Magnesium-Doped Lithium Niobate

    NASA Technical Reports Server (NTRS)

    Himmer, Phillip; Battle, Philip; Suckow, William; Switzer, Greg

    2011-01-01

    This work proposes to establish the feasibility of fabricating isolated ridge waveguides in 5% MgO:LN. Ridge waveguides in MgO:LN will significantly improve power handling and conversion efficiency, increase photonic component integration, and be well suited to spacebased applications. The key innovation in this effort is to combine recently available large, high-photorefractive-damage-threshold, z-cut 5% MgO:LN with novel ridge fabrication techniques to achieve high-optical power, low-cost, high-volume manufacturing of frequency conversion structures. The proposed ridge waveguide structure should maintain the characteristics of the periodically poled bulk substrate, allowing for the efficient frequency conversion typical of waveguides and the high optical damage threshold and long lifetimes typical of the 5% doped bulk substrate. The low cost and large area of 5% MgO:LN wafers, and the improved performance of the proposed ridge waveguide structure, will enhance existing measurement capabilities as well as reduce the resources required to achieve high-performance specifications. The purpose of the ridge waveguides in MgO:LN is to provide platform technology that will improve optical power handling and conversion efficiency compared to existing waveguide technology. The proposed ridge waveguide is produced using standard microfabrication techniques. The approach is enabled by recent advances in inductively coupled plasma etchers and chemical mechanical planarization techniques. In conjunction with wafer bonding, this fabrication methodology can be used to create arbitrarily shaped waveguides allowing complex optical circuits to be engineered in nonlinear optical materials such as magnesium doped lithium niobate. Researchers here have identified NLO (nonlinear optical) ridge waveguide structures as having suitable value to be the leading frequency conversion structures. Its value is based on having the low-cost fabrication necessary to satisfy the challenging pricing

  1. Submersible observations along the southern Juan de Fuca Ridge: 1984 Alvin program.

    USGS Publications Warehouse

    Normark, William R.; Morton, Janet L.; Ross, Stephanie L.

    1987-01-01

    In September 1984, the research submersible Alvin provided direct observations of three major hydrothermal vent areas along the southernmost segment of the Juan de Fuca Ridge (JFR). The submersible operations focused on specific volcanologie, structural, and hydrothermal problems that had been identified during the preceding 4 years of photographic, dredging, acoustic imaging, and geophysical studies along a 12-km-long section of the ridge. A continuously maintained (from 1981 to the present) net of seafloor-anchored acoustic transponders allowed the observations from Alvin to be directly tied to all previous U.S. Geological Survey data sets and National Oceanic and Atmospheric Administration water column surveys from 1984 to the present. The three vent areas studied are the largest of at least six areas identified by previous deep-towed camera surveys that lie within a deep cleft, which marks the axis of symmetry of the JFR in this region. The cleft appears to be the locus of eruption for this segment of the JFR. The vent areas, at least in part, are localized near what appear to be previous volcanic eruptive centers marked by extensive lava lake collapse features adjacent to the cleft at these sites. Each hydrothermal area has several active discharge sites, and sulfide deposits occur as clusters (15–100 m2) of small chimneys, individual large chimneys, or clusters of large branched chimneys. We review the dive program and present a brief synthesis of the geology of the vent sites together with sample and track line compilations.

  2. Lake whitefish diet, condition, and energy density in Lake Champlain and the lower four Great Lakes following dreissenid invasions

    USGS Publications Warehouse

    Herbst, Seth J.; Marsden, J. Ellen; Lantry, Brian F.

    2013-01-01

    Lake Whitefish Coregonus clupeaformis support some of the most valuable commercial freshwater fisheries in North America. Recent growth and condition decreases in Lake Whitefish populations in the Great Lakes have been attributed to the invasion of the dreissenid mussels, zebra mussels Dreissena polymorpha and quagga mussels D. bugensis, and the subsequent collapse of the amphipod, Diporeia, a once-abundant high energy prey source. Since 1993, Lake Champlain has also experienced the invasion and proliferation of zebra mussels, but in contrast to the Great Lakes, Diporeia were not historically abundant. We compared the diet, condition, and energy density of Lake Whitefish from Lake Champlain after the dreissenid mussel invasion to values for those of Lake Whitefish from Lakes Michigan, Huron, Erie, and Ontario. Lake Whitefish were collected using gill nets and bottom trawls, and their diets were quantified seasonally. Condition was estimated using Fulton's condition factor (K) and by determining energy density. In contrast to Lake Whitefish from some of the Great Lakes, those from Lake Champlain Lake Whitefish did not show a dietary shift towards dreissenid mussels, but instead fed primarily on fish eggs in spring, Mysis diluviana in summer, and gastropods and sphaeriids in fall and winter. Along with these dietary differences, the condition and energy density of Lake Whitefish from Lake Champlain were high compared with those of Lake Whitefish from Lakes Michigan, Huron, and Ontario after the dreissenid invasion, and were similar to Lake Whitefish from Lake Erie; fish from Lakes Michigan, Huron, and Ontario consumed dreissenids, whereas fish from Lake Erie did not. Our comparisons of Lake Whitefish populations in Lake Champlain to those in the Great Lakes indicate that diet and condition of Lake Champlain Lake Whitefish were not negatively affected by the dreissenid mussel invasion.

  3. Ridge-crossing mantle plumes and gaps in tracks

    NASA Astrophysics Data System (ADS)

    Sleep, Norman H.

    2002-12-01

    Hot spot tracks approach, cross, and leave ridge axes. The complications of this process make it difficult to determine the track followed by a plume and the evolution of its vigor. When a plume is sufficiently near the ridge axis, buoyant plume material flows along the base of the lithosphere toward the axis, forming an on-axis hot spot. The track of the on-axis hot spot is a symmetric V on both plates and an unreliable indication of the path followed by the plume. Aseismic ridges form more or less along flowlines from a plume to a ridge axis when channels form at the base of the lithosphere. A dynamic effect is that off-axis hot spots appear to shut off at the time that an on-axis hot spot becomes active along an axis-approaching track. This produces a gap in the obvious track and a jump of the hot spot to the ridge axis. The gap results from the effects of ponded plume material on intraplate (membrane) stress. Membrane tension lets dikes ascend efficiently to produce obvious tracks of edifices. An off-axis hot spot shuts down when the plume is sufficiently near the ridge axis that plume material flows there, putting the nearby lithosphere above the plume into compression, preventing dikes. In addition, the off-axis thickness of plume material, which produces membrane tension, decreases as the slope of the base of the lithosphere increases beneath young lithosphere. Slow spreading rates favor gaps produced in this way. Gaps are observed near both fast and slow ridges.

  4. Spatial patterns in PCB concentrations of Lake Michigan lake trout

    USGS Publications Warehouse

    Madenjian, Charles P.; DeSorcie, Timothy J.; Stedman, Ralph M.; Brown, Edward H.; Eck, Gary W.; Schmidt, Larry J.; Hesselberg, Robert J.; Chernyak, Sergei M.; Passino-Reader, Dora R.

    1999-01-01

    Most of the PCB body burden in lake trout (Salvelinus namaycush) of the Great Lakes is from their food. PCB concentrations were determined in lake trout from three different locations in Lake Michigan during 1994–1995, and lake trout diets were analyzed at all three locations. The PCB concentrations were also determined in alewife (Alosa pseudoharengus), rainbow smelt (Osmerus mordax), bloater (Coregonus hoyi), slimy sculpin (Cottus cognatus), and deepwater sculpin (Myoxocephalus thompsoni), five species of prey fish eaten by lake trout in Lake Michigan, at three nearshore sites in the lake. Despite the lack of significant differences in the PCB concentrations of alewife, rainbow smelt, bloater, slimy sculpin, and deepwater sculpin from the southeastern nearshore site near Saugatuck (Michigan) compared with the corresponding PCB concentrations from the northwestern nearshore site near Sturgeon Bay (Wisconsin), PCB concentrations in lake trout at Saugatuck were significantly higher than those at Sturgeon Bay. The difference in the lake trout PCB concentrations between Saugatuck and Sturgeon Bay could be explained by diet differences. The diet of lake trout at Saugatuck was more concentrated in PCBs than the diet of Sturgeon Bay lake trout, and therefore lake trout at Saugatuck were more contaminated in PCBs than Sturgeon Bay lake trout. These findings were useful in interpreting the long-term monitoring series for contaminants in lake trout at both Saugatuck and the Wisconsin side of the lake.

  5. Determinants of alveolar ridge preservation differ by anatomic location

    PubMed Central

    Leblebicioglu, Binnaz; Salas, Mabel; Ort, Yirae; Johnson, Ashley; Yildiz, Vedat O.; Kim, Do-Gyoon; Agarwal, Sudha; Tatakis, Dimitris N.

    2016-01-01

    Aim To investigate and compare outcomes following alveolar ridge preservation (ARP) in posterior maxilla and mandible. Methods Twenty-four patients (54 ± 3 years) with single posterior tooth extraction were included. ARP was performed with freeze-dried bone allograft and collagen membrane. Clinical parameters were recorded at extraction and re-entry. Harvested bone cores were analysed by microcomputed tomography (micro-CT), histomorphometry and immunohistochemistry. Results In both jaws, ARP prevented ridge height loss, but ridge width was significantly reduced by approximately 2.5 mm. Healing time, initial clinical attachment loss and amount of keratinized tissue at extraction site were identified as determinants of ridge height outcome. Buccal plate thickness and tooth root length were identified as determinants of ridge width outcome. In addition, initial ridge width was positively correlated with ridge width loss. Micro-CT revealed greater mineralization per unit volume in new bone compared with existing bone in mandible (p < 0.001). Distributions of residual graft, new cellular bone and immature tissue were similar in both jaws. Conclusion Within the limitations of this study, the results indicate that in different anatomic locations different factors may determine ARP outcomes. Further studies are needed to better understand determinants of ARP outcomes. PMID:23432761

  6. Alternative Fuels Data Center: Blue Ridge Parkway Incorporates Alternative

    Science.gov Websites

    Fuels in Its Fleet Blue Ridge Parkway Incorporates Alternative Fuels in Its Fleet to someone by E-mail Share Alternative Fuels Data Center: Blue Ridge Parkway Incorporates Alternative Fuels in Its Fleet on Facebook Tweet about Alternative Fuels Data Center: Blue Ridge Parkway Incorporates Alternative

  7. Potential strategies for recovery of lake whitefish and lake herring stocks in eastern Lake Erie

    USGS Publications Warehouse

    Oldenburg, K.; Stapanian, M.A.; Ryan, P.A.; Holm, E.

    2007-01-01

    Lake Erie sustained large populations of ciscoes (Salmonidae: Coregoninae) 120 years ago. By the end of the 19th century, abundance of lake whitefish (Coregonus clupeaformis) had declined drastically. By 1925, the lake herring (a cisco) population (Coregonus artedii) had collapsed, although a limited lake herring fishery persisted in the eastern basin until the 1950s. In the latter part of the 20th century, the composition of the fish community changed as oligotrophication proceeded. Since 1984, a limited recovery of lake whitefish has occurred, however no recovery was evident for lake herring. Current ecological conditions in Lake Erie probably will not inhibit recovery of the coregonine species. Recovery of walleye (Sander vitreus) and efforts to rehabilitate the native lake trout (Salvelinus namaycush) in Lake Erie will probably assist recovery because these piscivores reduce populations of alewife (Alosa psuedoharengus) and rainbow smelt (Osmerus mordax), which inhibit reproductive success of coregonines. Although there are considerable spawning substrates available to coregonine species in eastern Lake Erie, eggs and fry would probably be displaced by storm surge from most shoals. Site selection for stocking or seeding of eggs should consider the reproductive life cycle of the stocked fish and suitable protection from storm events. Two potential sites in the eastern basin have been identified. Recommended management procedures, including commercial fisheries, are suggested to assist in recovery. Stocking in the eastern basin of Lake Erie is recommended for both species, as conditions are adequate and the native spawning population in the eastern basin is low. For lake herring, consideration should be given to match ecophenotypes as much as possible. Egg seeding is recommended. Egg seeding of lake whitefish should be considered initially, with fingerling or yearling stocking suggested if unsuccessful. Spawning stocks of whitefish in the western basin of Lake

  8. Glacial lake inventory and lake outburst potential in Uzbekistan.

    PubMed

    Petrov, Maxim A; Sabitov, Timur Y; Tomashevskaya, Irina G; Glazirin, Gleb E; Chernomorets, Sergey S; Savernyuk, Elena A; Tutubalina, Olga V; Petrakov, Dmitriy A; Sokolov, Leonid S; Dokukin, Mikhail D; Mountrakis, Giorgos; Ruiz-Villanueva, Virginia; Stoffel, Markus

    2017-08-15

    Climate change has been shown to increase the number of mountain lakes across various mountain ranges in the World. In Central Asia, and in particular on the territory of Uzbekistan, a detailed assessment of glacier lakes and their evolution over time is, however lacking. For this reason we created the first detailed inventory of mountain lakes of Uzbekistan based on recent (2002-2014) satellite observations using WorldView-2, SPOT5, and IKONOS imagery with a spatial resolution from 2 to 10m. This record was complemented with data from field studies of the last 50years. The previous data were mostly in the form of inventories of lakes, available in Soviet archives, and primarily included localized in-situ data. The inventory of mountain lakes presented here, by contrast, includes an overview of all lakes of the territory of Uzbekistan. Lakes were considered if they were located at altitudes above 1500m and if lakes had an area exceeding 100m 2 . As in other mountain regions of the World, the ongoing increase of air temperatures has led to an increase in lake number and area. Moreover, the frequency and overall number of lake outburst events have been on the rise as well. Therefore, we also present the first outburst assessment with an updated version of well-known approaches considering local climate features and event histories. As a result, out of the 242 lakes identified on the territory of Uzbekistan, 15% are considered prone to outburst, 10% of these lakes have been assigned low outburst potential and the remainder of the lakes have an average level of outburst potential. We conclude that the distribution of lakes by elevation shows a significant influence on lake area and hazard potential. No significant differences, by contrast, exist between the distribution of lake area, outburst potential, and lake location with respect to glaciers by regions. Copyright © 2017 Elsevier B.V. All rights reserved.

  9. Curiosity at Gale Crater's Hematite Ridge: High Mn and P Near the Ridge Show Chemical Evidence for Generation by an Oxidation Front

    NASA Astrophysics Data System (ADS)

    Wiens, R. C.; Meslin, P. Y.; Lanza, N.; Frydenvang, J.; Mangold, N.; Johnson, J. R.; Fraeman, A. A.; Horgan, B.; Bedford, C.; Blaney, D. L.; Bridges, J.; Cousin, A.; Ehlmann, B. L.; Forni, O.; Gasda, P. J.; Gasnault, O.; Gellert, R.; Johnstone, S.; Lamm, S. N.; Lasue, J.; Le Mouelic, S.; Maurice, S.; Newsom, H. E.; Ollila, A.; Payre, V.; Rapin, W.; Salvatore, M. R.; Schwenzer, S. P.; Thomas, N. H.; Vasavada, A. R.

    2017-12-01

    After traversing >17 km, the Curiosity rover has reached Vera Rubin Ridge (VRR), formerly known as the Hematite Ridge. Situated 200 m above the base of Gale crater on the slope of Mt. Sharp, VRR was one of the original objectives of the mission. VRR stretches 6.5 km NE-SW with a vertical height of 30 m (to -4200 m), it is the largest surface feature encountered by Curiosity to date. Orbital observation by CRISM of relatively strong hematite signal along the ridge gave it its original name. Some hematite spectral signatures along the ridge have been observed by Curiosity from long distance by Mastcam and ChemCam passive spectra. Curiosity started observing local enrichments of hematite in Murray lacustrine sediments near Bagnold Dunes, which may or may not be related to the hematite observed on the ridge top. The presence of hematite-like spectral signatures became variable as the rover approached below the ridge. Chemistry and ridge imaging: Magnesium, Mn, and P have shown strong increases in dark surface features in some regions below the ridge. Manganese oxide abundances have risen to >10 wt. % in some dark nodules and laminae. Iron, Mg, and P appear correlated in high-P observations, with the highest values associated with vein-related inclusions. Another class of dark features shows high Fe without high Mn or P. ChemCam high-resolution imaging from within 100 m of the base of the ridge shows regions of both finely laminated parallel strata and low-angle cross stratification along with vertical fractures surrounded by alteration halos; these are comparable to Murray stratigraphy. Given that the exposed surface of the Murray formation is the result of significant erosional deflation, the ridge must be more erosionally resistant than the surrounding material. The observation of high-oxidation-potential element enrichments below VRR argues for an oxidation front in which the local sediments were enriched in oxidized iron (hematite) and manganese. In this

  10. Asymmetric sea-floor spreading caused by ridge-plume interactions

    NASA Astrophysics Data System (ADS)

    Müller, R. Dietmar; Roest, Walter R.; Royer, Jean-Yves

    1998-12-01

    Crustal accretion at mid-ocean ridges is generally modelled as a symmetric process. Regional analyses, however, often show either small-scale asymmetries, which vary rapidly between individual spreading corridors, or large-scale asymmetries represented by consistent excess accretion on one of the two separating plates over geological time spans. In neither case is the origin of the asymmetry well understood. Here we present a comprehensive analysis of the asymmetry of crustal accretion over the past 83Myr based on a set of self-consistent digital isochrons and models of absolute plate motion,. We find that deficits in crustal accretion occur mainly on ridge flanks overlying one or several hotspots. We therefore propose that asymmetric accretion is caused by ridge propagation towards mantle plumes or minor ridge jumps sustained by asthenospheric flow, between ridges and plumes. Quantifying the asymmetry of crustal accretion provides a complementary approach to that based on geochemical and other geophysical data, in helping to unravel how mantle plumes and mid-ocean ridges are linked through mantle convection processes.

  11. Progress toward lake trout restoration in Lake Michigan

    USGS Publications Warehouse

    Holey, Mark E.; Rybicki, Ronald W.; Eck, Gary W.; Brown, Edward H.; Marsden, J. Ellen; Lavis, Dennis S.; Toneys, Michael L.; Trudeau, Tom N.; Horrall, Ross M.

    1995-01-01

    Progress toward lake trout restoration in Lake Michigan is described through 1993. Extinction of the native lake trout fishery by sea lamprey predation, augmented by exploitation and habitat destruction, resulted in an extensive stocking program of hatchery-reared lake trout that began in 1965. Sea lamprey abundance was effectively controlled using selective chemical toxicants. The initial stocking produced a measurable wild year class of lake trout by 1976 in Grand Traverse Bay, but failed to continue probably due to excessive exploitation. The overall lack of successful reproduction lakewide by the late 1970s led to the development and implementation in 1985 of a focused inter-agency lakewide restoration plan by a technical committee created through the Lake Committee structure of the Great Lakes Fishery Commission. Strategies implemented in 1985 by the plan included setting a 40% total mortality goal lakewide, creating two large refuges designed to encompass historically the most productive spawning habitat and protect trout stocked over their home range, evaluating several lake trout strains, and setting stocking priorities throughout the lake. Target levels for stocking in the 1985 Plan have never been reached, and are much less than the estimated lakewide recruitment of yearlings by the native lake trout stocks. Since 1985, over 90% of the available lake trout have been stocked over the best spawning habitat, and colonization of the historically productive offshore reefs has occurred. Concentrations of spawning lake trout large enough for successful reproduction, based on observations of successful hatchery and wild stocks, have developed at specific reefs. Continued lack of recruitment at these specific sites suggests that something other than stotk abundance has limited success. Poor survival of lake trout eggs, assumed to be related to contaminant burden, occurred in the late 1970s and early 1980s, but survival has since increased to equal survival in the

  12. Lake trout rehabilitation in Lake Huron

    USGS Publications Warehouse

    Eshenroder, Randy L.; Payne, N. Robert; Johnson, James E.; Bowen, Charles; Ebener, Mark P.

    1995-01-01

    Efforts to restore lake trout (Salvelinus namaycush) in Lake Huron after their collapse in the 1940s were underway in the early 1970s with completion of the first round of lampricide applications in tributary streams and the stocking of several genotypes. We assess results of rehabilitation and establish a historical basis for comparison by quantifying the catch of spawning lake trout from Michigan waters in 1929-1932. Sixty-eight percent of this catch occurred in northern waters (MH-1) and most of the rest (15%) was from remote reefs in the middle of the main basin. Sea lampreys (Petromyzon marinus) increased in the early 1980s in the main basin and depressed spawning populations of lake trout. This increase was especially severe in northern waters and appeared to be associated with untreated populations in the St. Marys River. Excessive commercial fishing stemming from unresolved treaty rights also contributed to loss of spawning fish in northern Michigan waters. Seneca-strain lake trout did not appear to be attacked by sea lampreys until they reached a size > 532 mm. At sizes > 632 mm, Seneca trout were 40-fold more abundant than the Marquette strain in matched-planting experiments. Natural reproduction past the fry stage has occurred in Thunder Bay and South Bay, but prospects for self-sustaining populations of lake trout in the main basin are poor because sea lampreys are too abundant, only one side of the basin is stocked, and stocking is deferred to allow commercial gillnetting in areas where most of the spawning occurred historically. Backcross lake trout, a lake trout x splake (s. Fontinalis x s. Namaycush) hybrid, did not reproduce in Georgian Bay, but this genotype is being replaced with pure-strain lake trout, whose early performance appears promising.

  13. Sulfate reduction controlled by organic matter availability in deep sediment cores from the saline, alkaline Lake Van (Eastern Anatolia, Turkey)

    PubMed Central

    Glombitza, Clemens; Stockhecke, Mona; Schubert, Carsten J.; Vetter, Alexandra; Kallmeyer, Jens

    2013-01-01

    As part of the International Continental Drilling Program deep lake drilling project PaleoVan, we investigated sulfate reduction (SR) in deep sediment cores of the saline, alkaline (salinity 21.4‰, alkalinity 155 m mEq-1, pH 9.81) Lake Van, Turkey. The cores were retrieved in the Northern Basin (NB) and at Ahlat Ridge (AR) and reached a maximum depth of 220 m. Additionally, 65–75 cm long gravity cores were taken at both sites. SR rates (SRR) were low (≤22 nmol cm-3 day-1) compared to lakes with higher salinity and alkalinity, indicating that salinity and alkalinity are not limiting SR in Lake Van. Both sites differ significantly in rates and depth distribution of SR. In NB, SRR are up to 10 times higher than at AR. SR could be detected down to 19 mblf (meters below lake floor) at NB and down to 13 mblf at AR. Although SRR were lower at AR than at NB, organic matter (OM) concentrations were higher. In contrast, dissolved OM in the pore water at AR contained more macromolecular OM and less low molecular weight OM. We thus suggest, that OM content alone cannot be used to infer microbial activity at Lake Van but that quality of OM has an important impact as well. These differences suggest that biogeochemical processes in lacustrine sediments are reacting very sensitively to small variations in geological, physical, or chemical parameters over relatively short distances. PMID:23908647

  14. DISTINCTIVE FINE-SCALE MORPHOLOGY OF HYDRATE RIDGE

    NASA Astrophysics Data System (ADS)

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

    2009-12-01

    High-resolution multibeam bathymetry (vertical precision of 0.15 m and horizontal resolution of 1.0 m) collected using an autonomous underwater vehicle (AUV) reveals in unprecedented detail the fine-scale morphology of the ridge crests on Hydrate Ridge, offshore Oregon. An inertial navigation system combined with a doppler velocity sonar allowed the AUV to fly pre-programmed grids with 150 m line spacing at 3 knots while maintaining an altitude of 50 m above the bottom. The data were collected on two 17.5-hour-long dives, one covering a 4.3 x 1.9 km area on the southern crest of Hydrate Ridge (769 to 930 m water depths) and the other covering a 5.2 x 2 km area on the northern crest of Hydrate Ridge (584 to 985 m water depths). These surveys cover the seafloor associated with gas hydrate research boreholes at ODP Sites 891 and 1245 to 1250). The southern crest of Hydrate Ridge is an area being considered for a cable-connected seafloor observatory. The surface of southern Hydrate Ridge is generally smooth except for two approximately circular patches with maximum diameters of 350 m and 500 m associated with a distinctive hummocky topography. The geometric relationships indicate that the edges of these patches are surrounded with small apparently erosional scarps and thus the strata exposed within the patches are stratigraphically lower than the surrounding smooth seafloor. The fine scale-topography within these patches is characterized by a highly irregular surface formed by small, sometimes circular ~0.5 m deep pits, local highs and lows separated by ~0.5 high ledges that could be formed by irregularly eroded bedding surfaces. Similar shapes also occur at larger scales. For example, a previously described feature called the “pinnacle” is a ~15 m topographic high in the center of one of these hummocky patches. The surface of northern Hydrate Ridge has similar patches of hummocky topography. However, the patches are more numerous, associated with greater relief

  15. Topography and tectonics of mid-oceanic ridge axes

    NASA Technical Reports Server (NTRS)

    Sleep, N. H.; Rosendahl, B. R.

    1979-01-01

    Numerical fluid dynamic models of mid-oceanic ridge axes were constructed using distributions of material properties constrained by seismic studies and thermal calculations. The calculations indicate that spreading is passive except for forces caused by density differences due to thermal expansion and partial melt. Except for geometric differences due to temperature distribution, one set of mechanical properties can adequately explain central rifts of slow ridges and central peaks of fast ridges. Viscous head loss in the upwelling material dominates at low spreading rates where material ascends through a narrow conduit. Thermal expansion and partial melting dominate at high spreading rates where a wide low viscosity crustal magma chamber is present. The preferred rheology is 10 to the 20th poise for the upwelling lithosphere; less than 5 x 10 to the 17th for the crustal magma chamber and axial intrusion zone at fast ridges, and a yield stress of 200 bars for the lithosphere. The calculation correctly predicts the existence of central peaks at 'hot-spot' ridges, where seismic evidence indicates a large magma chamber.

  16. Evolution of alkaline lakes - Lake Van case study

    NASA Astrophysics Data System (ADS)

    Tillman Meyer, Felix; Viehberg, Finn; Bahroun, Sonya; Wolf, Annabel; Immenhauser, Adrian; Kwiecien, Ola

    2017-04-01

    Lake Van in Eastern Anatolia (Turkey) is the largest terminal soda lake on Earth. The lake sedimentary profile covers ca. 600 ka (Stockhecke et al. 2014) Based on lithological changes, the presence of freshwater microfossils and close-to-freshwater pH value in the pore water, members of ICDP PALEOVAN concluded that Lake Van might have started as an open lake. Here we show paleontological and geochemical evidence in favour of this idea and constrain the time, when Lake Van likely transformed into a closed lake. Additionally we provide the first conceptual model of how this closure may have happened. Our archives of choice are inorganic and biogenic carbonates, separated by wet sieving. We identified microfossil assemblages (fraction > 125 µm) and performed high-resolution oxygen isotope (delta18O) and elemental (Mg/Ca, Sr/Ca) analyses of the fraction < 63 µm assuming that it represents only carbonates precipitating in the water column. Microfossil assemblage consists of three different species of ostracods (Candona spp, Loxoconcha sp, Amnicythere spp.), diatoms, gastropods and bivalves. Brakish-water ostracods, Loxoconcha sp and Amnicythere sp occur more often after 530 ka. Additionaly, Loxoconcha sp is a shallow-water species relaying on plants growing in the photic zone as food supply. These two aspects point to an increasing salinity in a shallowing lake. The delta18O values of inorganic carbonates are relatively low during the initial phase of Lake Van and increase abruptly (ca. 7‰) after 530 ka BP. At approximately the same time combination of Sr/Ca and Mg/Ca data suggest first occurrence of aragonite. Again, these findings suggest geochemical changes of the lake water concurrent with transition documented by microfossils. Comparison between Lake Van and Lake Ohrid (Lacey et al. 2016) delta18O data, precludes regional climate change (e.g.: increased evaporation) as the main driver of observed changes. With no evidence for increased volcanic or tectonic

  17. 1. GENERAL VIEW OF ENTRANCE TO BLUE RIDGE TUNNEL (LEFT) ...

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

    1. GENERAL VIEW OF ENTRANCE TO BLUE RIDGE TUNNEL (LEFT) FROM SOUTHEAST. ORIGINAL BLUE RIDGE R.R. (CROZET) TUNNEL IS VISIBLE AT RIGHT. - Chesapeake & Ohio Railroad, Blue Ridge Tunnel, Highway 250 at Rockfish Gap, Afton, Nelson County, VA

  18. Temporal and spatial distribution of endangered juvenile Lost River and shortnose suckers in relation to environmental variables in Upper Klamath Lake, Oregon: 2009 annual data summary

    USGS Publications Warehouse

    Bottcher, Jared L.; Burdick, Summer M.

    2010-01-01

    Lost River sucker (Deltistes luxatus) and shortnose sucker (Chasmistes brevirostris) were listed as endangered in 1988 for a variety of reasons including apparent recruitment failure. Upper Klamath Lake, Oregon, and its tributaries are considered the most critical remaining habitat for these two species. Age-0 suckers are often abundant in Upper Klamath Lake throughout the summer months, but catches decline dramatically between late August and early September each year. Similar declines of age-1 suckers between spring and late summer also occur annually. These rapid declines in catch rates and a lack of substantial recruitment into adult sucker populations in recent years suggests sucker populations experience high mortality between their first summer and first spawn. Summer age-0 sucker habitat use and distribution have been studied extensively, but many uncertainties remain about age-1 and older juvenile habitat use, distribution, and movement patterns within Upper Klamath Lake. This study was designed to examine seasonal changes in distribution of age-1 suckers in Upper Klamath Lake as they relate to depth and water quality. The results of our third annual spring and summer sampling effort are presented in this report. Catch data collected in 2009 indicate seasonal changes in age-1 and older juvenile sucker habitat use coincident with changes in water quality. Although age-1 sucker catch rates were again concentrated along the western shore in June and early July, as they were in 2007 and 2008, very few age-1 suckers were captured in Eagle Ridge Trench in 2009 - a deepwater area along the western shore extending from Howard Bay to Eagle Ridge Point. Instead, suckers in 2009 were concentrated in the relatively shallow bays along the western shore. Nevertheless, as dissolved-oxygen concentrations decreased in mid-July below sublethal thresholds around the Eagle Ridge Trench, age-1 suckers apparently moved away from the western shore, and subsequently were captured

  19. Embryotoxicity of an extract from Great Lakes lake trout to rainbow trout and lake trout

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Wright, P.J.; Tillitt, D.E.

    1995-12-31

    Aquatic ecosystems such as the Great Lakes are known to be contaminated with chemicals that are toxic to fish. However, the role of these contaminants in reproductive failures of fishes, such as lake trout recruitment, has remained controvertible. It was the objective to evaluate dioxin-like embryotoxicity of a complex mixture of chemicals and predict their potential to cause the lack of recruitment in Great Lakes lake trout. Graded doses of a complex environmental extract were injected into eggs of both rainbow trout and lake trout. The extract was obtained from whole adult lake trout collected from Lake Michigan in 1988.more » The extract was embryotoxic in rainbow trout, with LD50 values for Arlee strain and Erwin strain of 33 eggEQ and 14 eggEQ respectively. The LOAEL for hemorrhaging, yolk-sac edema, and craniofacial deformities in rainbow trout were 2, 2, and 4 eggEQ, respectively. Subsequent injections of the extract into lake trout eggs were likewise embryotoxic, with an LD50 value of 7 eggEQ. The LOAEL values for the extract in lake trout for hemorrhaging, yolk-sac edema, and craniofacial deformities were 0.1, 1, and 2 eggEQ, respectively. The current levels of contaminants in lake trout eggs are above the threshold for hemorrhaging and yolk-sac edema. The results also support the use of an additive model of toxicity to quantify PCDDs, PCDFs, Non-o-PCBs, and Mono-o-PCBs in relation to early life stage mortality in Lake Michigan lake trout.« less

  20. Hydrogeologic Controls on Lake Level at Mountain Lake, Virginia

    NASA Astrophysics Data System (ADS)

    Roningen, J. M.; Burbey, T. J.

    2011-12-01

    Mountain Lake in Giles County, Virginia has a documented history of severe natural lake-level changes involving groundwater seepage that extend over the past 4200 years. Featured in the 1986 movie Dirty Dancing, the natural lake dried up completely in September 2008 and levels have not yet recovered. A hydrogeologic investigation was undertaken in an effort to determine the factors influencing lake level changes. A daily water balance, dipole-dipole electrical resistivity surveying, well logging and chemical sampling have shed light on: 1) the influence of a fault not previously discussed in literature regarding the lake, 2) the seasonal response to precipitation of a forested first-order drainage system in fractured rock, and 3) the possibility of flow pathways related to karst features. Geologic controls on lake level were investigated using several techniques. Geophysical surveys using dipole-dipole resistivity located possible subsurface flowpaths both to and from the lake. Well logs, lineament analysis, and joint sampling were used to assess structural controls on lake hydrology. Major ions were sampled at wells, springs, streams, and the lake to evaluate possible mixing of different sources of water in the lake. Groundwater levels were monitored for correlation to lake levels, rainfall events, and possible seismic effects. The hydrology of the lake was quantified with a water balance on a daily time step. Results from the water balance indicate steady net drainage and significant recharge when vegetation is dormant, particularly during rain-on-snow melt events. The resistivity survey reveals discrete areas that represent flow pathways from the lake, as well as flowpaths to springs upgradient of the lake located in the vicinity of the fault. The survey also suggests that some flowpaths may originate outside of the topographic watershed of the lake. Chemical evidence indicates karst may underlie the lakebed. Historical data suggest that artificial intervention

  1. Lake-level frequency analysis for Devils Lake, North Dakota

    USGS Publications Warehouse

    Wiche, Gregg J.; Vecchia, Aldo V.

    1996-01-01

    Two approaches were used to estimate future lake-level probabilities for Devils Lake. The first approach is based on an annual lake-volume model, and the second approach is based on a statistical water mass-balance model that generates seasonal lake volumes on the basis of seasonal precipitation, evaporation, and inflow. Autoregressive moving average models were used to model the annual mean lake volume and the difference between the annual maximum lake volume and the annual mean lake volume. Residuals from both models were determined to be uncorrelated with zero mean and constant variance. However, a nonlinear relation between the residuals of the two models was included in the final annual lakevolume model.Because of high autocorrelation in the annual lake levels of Devils Lake, the annual lake-volume model was verified using annual lake-level changes. The annual lake-volume model closely reproduced the statistics of the recorded lake-level changes for 1901-93 except for the skewness coefficient. However, the model output is less skewed than the data indicate because of some unrealistically large lake-level declines. The statistical water mass-balance model requires as inputs seasonal precipitation, evaporation, and inflow data for Devils Lake. Analysis of annual precipitation, evaporation, and inflow data for 1950-93 revealed no significant trends or long-range dependence so the input time series were assumed to be stationary and short-range dependent.Normality transformations were used to approximately maintain the marginal probability distributions; and a multivariate, periodic autoregressive model was used to reproduce the correlation structure. Each of the coefficients in the model is significantly different from zero at the 5-percent significance level. Coefficients relating spring inflow from one year to spring and fall inflows from the previous year had the largest effect on the lake-level frequency analysis.Inclusion of parameter uncertainty in the model

  2. Lake-level frequency analysis for Devils Lake, North Dakota

    USGS Publications Warehouse

    Wiche, Gregg J.; Vecchia, Aldo V.

    1995-01-01

    Two approaches were used to estimate future lake-level probabilities for Devils Lake. The first approach is based on an annual lake-volume model, and the second approach is based on a statistical water mass-balance model that generates seasonal lake volumes on the basis of seasonal precipitation, evaporation, and inflow.Autoregressive moving average models were used to model the annual mean lake volume and the difference between the annual maximum lake volume and the annual mean lake volume. Residuals from both models were determined to be uncorrelated with zero mean and constant variance. However, a nonlinear relation between the residuals of the two models was included in the final annual lake-volume model.Because of high autocorrelation in the annual lake levels of Devils Lake, the annual lakevolume model was verified using annual lake-level changes. The annual lake-volume model closely reproduced the statistics of the recorded lake-level changes for 1901-93 except for the skewness coefficient However, the model output is less skewed than the data indicate because of some unrealistically large lake-level declines.The statistical water mass-balance model requires as inputs seasonal precipitation, evaporation, and inflow data for Devils Lake. Analysis of annual precipitation, evaporation, and inflow data for 1950-93 revealed no significant trends or long-range dependence so the input time series were assumed to be stationary and short-range dependent.Normality transformations were used to approximately maintain the marginal probability distributions; and a multivariate, periodic autoregressive model was used to reproduce the correlation structure. Each of the coefficients in the model is significantly different from zero at the 5-percent significance level. Coefficients relating spring inflow from one year to spring and fall inflows from the previous year had the largest effect on the lake-level frequency analysis.Inclusion of parameter uncertainty in the model

  3. Lake trout in northern Lake Huron spawn on submerged drumlins

    USGS Publications Warehouse

    Riley, Stephen C.; Binder, Thomas; Wattrus, Nigel J.; Faust, Matthew D.; Janssen, John; Menzies, John; Marsden, J. Ellen; Ebener, Mark P.; Bronte, Charles R.; He, Ji X.; Tucker, Taaja R.; Hansen, Michael J.; Thompson, Henry T.; Muir, Andrew M.; Krueger, Charles C.

    2014-01-01

    Recent observations of spawning lake trout Salvelinus namaycush near Drummond Island in northern Lake Huron indicate that lake trout use drumlins, landforms created in subglacial environments by the action of ice sheets, as a primary spawning habitat. From these observations, we generated a hypothesis that may in part explain locations chosen by lake trout for spawning. Most salmonines spawn in streams where they rely on streamflows to sort and clean sediments to create good spawning habitat. Flows sufficient to sort larger sediment sizes are generally lacking in lakes, but some glacial bedforms contain large pockets of sorted sediments that can provide the interstitial spaces necessary for lake trout egg incubation, particularly if these bedforms are situated such that lake currents can penetrate these sediments. We hypothesize that sediment inclusions from glacial scavenging and sediment sorting that occurred during the creation of bedforms such as drumlins, end moraines, and eskers create suitable conditions for lake trout egg incubation, particularly where these bedforms interact with lake currents to remove fine sediments. Further, these bedforms may provide high-quality lake trout spawning habitat at many locations in the Great Lakes and may be especially important along the southern edge of the range of the species. A better understanding of the role of glacially-derived bedforms in the creation of lake trout spawning habitat may help develop powerful predictors of lake trout spawning locations, provide insight into the evolution of unique spawning behaviors by lake trout, and aid in lake trout restoration in the Great Lakes.

  4. Fuzzy and process modelling of contour ridge water dynamics

    NASA Astrophysics Data System (ADS)

    Mhizha, Alexander; Ndiritu, John

    2018-05-01

    Contour ridges are an in-situ rainwater harvesting technology developed initially for soil erosion control but are currently also widely promoted for rainwater harvesting. The effectiveness of contour ridges depends on geophysical, hydro-climatic and socio economic factors that are highly varied in time and space. Furthermore, field-scale data on these factors are often unavailable. This together with the complexity of hydrological processes at field scale limits the application of classical distributed process modelling to highly-instrumented experimental fields. This paper presents a framework that combines fuzzy logic and process-based approach for modelling contour ridges for rainwater harvesting where detailed field data are not available. Water balance for a representative contour-ridged field incorporating the water flow processes across the boundaries is integrated with fuzzy logic to incorporate the uncertainties in estimating runoff. The model is tested using data collected during the 2009/2010 and 2010/2011 rainfall seasons from two contour-ridged fields in Zhulube located in the semi-arid parts of Zimbabwe. The model is found to replicate soil moisture in the root zone reasonably well (NSE = 0.55 to 0.66 and PBIAS = -1.3 to 6.1 %). The results show that combining fuzzy logic and process based approaches can adequately model soil moisture in a contour ridged-field and could help to assess the water dynamics in contour ridged fields.

  5. Lake sturgeon population characteristics in Rainy Lake, Minnesota and Ontario

    USGS Publications Warehouse

    Adams, W.E.; Kallemeyn, L.W.; Willis, D.W.

    2006-01-01

    Rainy Lake contains a native population of lake sturgeon Acipenser fulvescens that has been largely unstudied. The aims of this study were to document the population characteristics of lake sturgeon in Rainy Lake and to relate environmental factors to year-class strength for this population. Gill-netting efforts throughout the study resulted in the capture of 322 lake sturgeon, including 50 recaptures. Lake sturgeon in Rainy Lake was relatively plump and fast growing compared with a 32-population summary. Population samples were dominated by lake sturgeon between 110 and 150 cm total length. Age–structure analysis of the samples indicated few younger (<10 years) lake sturgeon, but the smallest gill net mesh size used for sampling was 102 mm (bar measure) and would not retain small sturgeon. Few lake sturgeon older than age 50 years were captured, and maximum age of sampled fish was 59 years. Few correlations existed between lake sturgeon year-class indices and both annual and monthly climate variables, except that mean June air temperature was positively correlated with year-class strength. Analysis of Rainy Lake water elevation and resulting lake sturgeon year-class strength indices across years yielded consistent but weak negative correlations between late April and early June, when spawning of lake sturgeon occurs. The baseline data collected in this study should allow Rainy Lake biologists to establish more specific research questions in the future.

  6. Cenozoic tectono-thermal history of the Tordrillo Mountains, Alaska: Paleocene-Eocene ridge subduction, decreasing relief, and late Neogene faulting

    USGS Publications Warehouse

    Benowitz, Jeff A.; Haeussler, Peter J.; Layer, Paul W.; O'Sullivan, Paul B.; Wallace, Wes K.; Gillis, Robert J.

    2012-01-01

    Topographic development inboard of the continental margin is a predicted response to ridge subduction. New thermochronology results from the western Alaska Range document ridge subduction related orogenesis. K-feldspar thermochronology (KFAT) of bedrock samples from the Tordrillo Mountains in the western Alaska Range complement existing U-Pb, 40Ar/39Ar and AFT (apatite fission track) data to provide constraints on Paleocene pluton emplacement, and cooling as well as Late Eocene to Miocene vertical movements and exhumation along fault-bounded blocks. Based on the KFAT analysis we infer rapid exhumation-related cooling during the Eocene in the Tordrillo Mountains. Our KFAT cooling ages are coeval with deposition of clastic sediments in the Cook Inlet, Matanuska Valley and Tanana basins, which reflect high-energy depositional environments. The Tordrillo Mountains KFAT cooling ages are also the same as cooling ages in the Iliamna Lake region, the Kichatna Mountains of the western Alaska Range, and Mt. Logan in the Wrangell-St. Elias Mountains, thus rapid cooling at this time encompasses a broad region inboard of, and parallel to, the continental margin extending for several hundred kilometers. We infer these cooling events and deposition of clastic rocks are related to thermal effects that track the eastward passage of a slab window in Paleocene-Eocene time related to the subduction of the proposed Resurrection-Kula spreading ridge. In addition, we conclude that the reconstructed KFATmax negative age-elevation relationship is likely related to a long period of decreasing relief in the Tordrillo Mountains.

  7. Multiple expressions of plume-ridge interaction in the Galápagos: Volcanic lineaments and ridge jumps

    NASA Astrophysics Data System (ADS)

    Mittelstaedt, E.; Soule, S.; Harpp, K.; Fornari, D.; McKee, C.; Tivey, M.; Geist, D.; Kurz, M. D.; Sinton, C.; Mello, C.

    2012-05-01

    Anomalous volcanism and tectonics between near-ridge mantle plumes and mid-ocean ridges provide important insights into the mechanics of plume-lithosphere interaction. We present new observations and analysis of multibeam, side scan sonar, sub-bottom chirp, and total magnetic field data collected during the R/V Melville FLAMINGO cruise (MV1007; May-June, 2010) to the Northern Galápagos Volcanic Province (NGVP), the region between the Galápagos Archipelago and the Galápagos Spreading Center (GSC) on the Nazca Plate, and to the region east of the Galápagos Transform Fault (GTF) on the Cocos Plate. The NGVP exhibits pervasive off-axis volcanism related to the nearby Galápagos hot spot, which has dominated the tectonic evolution of the region. Observations indicate that ˜94% of the excess volcanism in our survey area occurs on the Nazca Plate in three volcanic lineaments. Identified faults in the NGVP are consistent with normal ridge spreading except for those within a ˜60 km wide swath of transform-oblique faults centered on the GTF. These transform-oblique faults are sub-parallel to the elongation direction of larger lineament volcanoes, suggesting that lineament formation is influenced by the lithospheric stress field. We evaluate current models for lineament formation using existing and new observations as well as numerical models of mantle upwelling and melting. The data support a model where the lithospheric stress field controls the location of volcanism along the lineaments while several processes likely supply melt to these eruptions. Synthetic magnetic models and an inversion for crustal magnetization are used to determine the tectonic history of the study area. Results are consistent with creation of the GTF by two southward ridge jumps, part of a series of jumps that have maintained a plume-ridge separation distance of 145 km to 215 km since ˜5 Ma.

  8. Modeling an exogenic origin for the equatorial ridge on Iapetus

    NASA Astrophysics Data System (ADS)

    Stickle, Angela M.; Roberts, James H.

    2018-06-01

    Iapetus has a ridge along the equator that extends continuously for more than 110° in longitude. Parts of the ridge rise as much as 20 km above the surrounding terrains. Most models for the formation of this enigmatic ridge are endogenic, generally requiring the formation of a fast-spinning Iapetus with an oblate shape due to the rotation speed. Many of these require specific scenarios and have constraining parameters in order to generate a ridge comparable to what is seen today. An exogenic formation mechanism has also been proposed, that the ridge represents the remains of an early ring system around Iapetus that collapsed onto the surface. Thus far, none of the models have conclusively identified the origin of the ridge. In this study, an exogenic origin for the ridge is assumed, which is derived from a collapsing disk of debris around Iapetus, without invoking any specific model for the generation of the debris disk. Here, we evaluate whether it is possible to generate a ridge of the size and shape as observed by simulating the impact of the collapsing debris using the CTH hydrocode. Pi-scaling calculations suggest that extremely oblique impact angles (1°-10°) are needed to add to ridge topography. These extreme impact angles severely reduce the cratering efficiency compared to a vertical impact, adding material rather than eroding it during crater formation. Furthermore, material is likely to be excavated at low angles, enhancing downrange accumulation. Multiple impacts from debris pieces will heighten this effect. Because infalling debris is predicted to impact at extremely low angles, both of these effects might have contributed to ridge formation on Iapetus. The extreme grazing angles of the impacts modeled here decouple much of the projectile energy from the target, and impact heating of the surface is not significant. These models suggest that a collapsing disk of debris should have been able to build topography to create a ridge around Iapetus.

  9. Oak Ridge reservation land-use plan

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Bibb, W. R.; Hardin, T. H.; Hawkins, C. C.

    1980-03-01

    This study establishes a basis for long-range land-use planning to accommodate both present and projected DOE program requirements in Oak Ridge. In addition to technological requirements, this land-use plan incorporates in-depth ecological concepts that recognize multiple uses of land as a viable option. Neither environmental research nor technological operations need to be mutually exclusive in all instances. Unique biological areas, as well as rare and endangered species, need to be protected, and human and environmental health and safety must be maintained. The plan is based on the concept that the primary use of DOE land resources must be to implementmore » the overall DOE mission in Oak Ridge. This document, along with the base map and overlay maps, provides a reasonably detailed description of the DOE Oak Ridge land resources and of the current and potential uses of the land. A description of the land characteristics, including geomorphology, agricultural productivity and soils, water courses, vegetation, and terrestrial and aquatic animal habitats, is presented to serve as a resource document. Essentially all DOE land in the Oak Ridge area is being fully used for ongoing DOE programs or has been set aside as protected areas.« less

  10. Structure of the Malpelo Ridge (Colombia) from seismic and gravity modelling

    NASA Astrophysics Data System (ADS)

    Marcaillou, Boris; Charvis, Philippe; Collot, Jean-Yves

    2006-12-01

    Wide-angle and multichannel seismic data collected on the Malpelo Ridge provide an image of the deep structure of the ridge and new insights on its emplacement and tectonic history. The crustal structure of the Malpelo Ridge shows a 14 km thick asymmetric crustal root with a smooth transition to the oceanic basin southeastward, whereas the transition is abrupt beneath its northwestern flank. Crustal thickening is mainly related to the thickening of the lower crust, which exhibits velocities from 6.5 to 7.4 km/s. The deep structure is consistent with emplacement at an active spreading axis under a hotspot like the present-day Galapagos Hotspot on the Cocos-Nazca Spreading Centre. Our results favour the hypothesis that the Malpelo Ridge was formerly a continuation of the Cocos Ridge, emplaced simultaneously with the Carnegie Ridge at the Cocos-Nazca Spreading Centre, from which it was separated and subsequently drifted southward relative to the Cocos Ridge due to differential motion along the dextral strike-slip Panama Fracture Zone. The steep faulted northern flank of the Malpelo Ridge and the counterpart steep and faulted southern flank of Regina Ridge are possibly related to a rifting phase that resulted in the Coiba Microplate’s separation from the Nazca Plate along the Sandra Rift.

  11. Melt distribution along the axis of ultraslow spreading mid-ocean ridges

    NASA Astrophysics Data System (ADS)

    Schlindwein, V. S. N.; Schmid, F.; Meier, M.

    2017-12-01

    Ultraslow spreading mid-ocean ridges (<15 mm/y full spreading rate) differ from faster spreading ridges by their uneven melt distribution. Crustal thickness varies along axis from zero to more than 8 km at volcanic centers. These volcanic centers receive more melt than the regional average and may be sustained for millions of years. The segmentation pattern and active volcanism at ultraslow spreading ridges greatly differs from faster spreading ridges. Using networks of ocean bottom seismometers at three differing ridge segments, we could show that the maximum depth of brittle faulting, equivalent approximately to temperatures of 600-700°C, varies drastically along axis. Ridge sections that lack an igneous crust exhibit a thick lithosphere as evidenced by the deepest mid-ocean ridge earthquakes observed so far at more than 30 km depth. Beneath areas of basalt exposure, in particular beneath pronounced volcanic centers, the axial lithosphere may be more than 15 km thinner allowing for melt flow at the base of the lithosphere towards the volcanoes, a process that has been postulated to explain the uneven along-axis melt distribution. Spreading events at ultraslow spreading ridges are unusual as we found from two spreading episodes at 85°E Gakkel Ridge and Segment 8 volcano on the Southwest Indian Ridge. These eruptions were preceded or accompanied by large (M>5) and long-lasting earthquake swarms and active magmatism lasted over 3-16 years. A massive hydrothermal event plume and sounds from deep submarine explosive volcanism were observed at Gakkel Ridge. At the Segment 8 volcano, we imaged a melt reservoir extending to about 8 km depth below the volcano that potentially fed a sill intrusion recorded by an ocean bottom seismometers about 30 km away at a neighboring subordinate volcanic center. To better understand the segmentation and melt transport at ultraslow spreading rigdes, we recently conducted a segment-scale seismicity survey of Knipovich Ridge in the

  12. Lake Level Variation in Small Lakes: Not a Clear Picture

    NASA Astrophysics Data System (ADS)

    Starratt, S.

    2017-12-01

    Lake level is a useful tool for identifying regional changes in precipitation and evaporation. Due to the volume of water in large lakes, they may only record large-scale changes in water balance, while smaller lakes may record more subtle variations. However, the record of water level in small lakes is affected by a number of factors including elevation, bathymetry, nutrient load, and aquatic macrophyte abundance. The latest Quaternary diatom records from three small lakes with areas of <10 ha (Hobart Lake, OR, 1458 masl; Swamp Lake, CA, 1554 masl; Favre Lake, NV, 2899 masl) and a larger lake (Medicine Lake, CA, 2036 masl, 154 ha) were compared in this study. All the lakes have a deep central basin (>10 m) surrounded by a shallow (1-2 m) shelf. Changes in the abundance of diatoms representing different life habits (benthic, tychoplanktic, planktic) were used to identify lake level variation. Benthic taxa dominate the assemblage when only the central basin is occupied. As the shallow shelf is flooded, the abundance of tychoplanktic taxa increases. Planktic taxa increase with the establishment of stratification. Favre Lake presents the clearest indication of initial lake level rise (7600-5750 cal yr BP) and intermittent flooding of the shelf for the remainder of the record. Stratification appears to become established only in the last few hundred years. Higher nutrient levels in the early part of the Hobart Lake record lead to a nearly monotypic planktic assemblage which is replaced by a tychoplanktic-dominated assemblage as the lake floods the shelf at about 3500 cal yr BP. The last 500 years is dominated by benthic taxa associated with aquatic macrophytes. The consistent presence of planktic taxa in the Swamp Lake record suggests that the lake was stratified during most of its history, although slight variations in the relative abundances of planktic and tychoplanktic groups occur. The Medicine Lake record shows a gradual increase in planktic species between 11

  13. Custom Titanium Ridge Augmentation Matrix (CTRAM): A Case Report.

    PubMed

    Connors, Christopher A; Liacouras, Peter C; Grant, Gerald T

    2016-01-01

    This is a case report of a custom titanium ridge augmentation matrix (CTRAM). Using cone beam computed tomography (CBCT), a custom titanium space-maintaining device was developed. Alveolar ridges were virtually augmented, a matrix was virtually designed, and the CTRAM was additively manufactured with titanium (Ti6Al4V). Two cases are presented that resulted in sufficient increased horizontal bone volume with successful dental implant placement. The CTRAM design allows for preoperative planning for increasing alveolar ridge dimensions to support dental implants, reduces surgical time, and prevents the need for a second surgical site to gain sufficient alveolar ridge bone volume for dental implant therapy.

  14. 78 FR 53675 - Safety Zone; Lake Erie Heritage Foundation, Battle of Lake Erie Reenactment; Lake Erie, Put-in...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-08-30

    ...-AA00 Safety Zone; Lake Erie Heritage Foundation, Battle of Lake Erie Reenactment; Lake Erie, Put-in-Bay... temporary safety zone in the waters of Lake Erie in the vicinity of Put-In-Bay, OH. This safety zone is intended to restrict vessels from a portion of Lake Erie during Battle of Lake Erie Reenactment near Put-In...

  15. Normalization Ridge Regression in Practice I: Comparisons Between Ordinary Least Squares, Ridge Regression and Normalization Ridge Regression.

    ERIC Educational Resources Information Center

    Bulcock, J. W.

    The problem of model estimation when the data are collinear was examined. Though the ridge regression (RR) outperforms ordinary least squares (OLS) regression in the presence of acute multicollinearity, it is not a problem free technique for reducing the variance of the estimates. It is a stochastic procedure when it should be nonstochastic and it…

  16. Hydrodynamic role of longitudinal ridges in a leatherback turtle swimming

    NASA Astrophysics Data System (ADS)

    Bang, Kyeongtae; Kim, Jooha; Lee, Sang-Im; Choi, Haecheon

    2015-11-01

    The leatherback sea turtle (Dermochelys coriacea), the fastest swimmer and the deepest diver among marine turtles, has five longitudinal ridges on its carapace. These ridges are the most remarkable morphological features distinguished from other marine turtles. To investigate the hydrodynamic role of these ridges in the leatherback turtle swimming, we model a carapace with and without ridges by using three dimensional surface data of a stuffed leatherback turtle in the National Science Museum, Korea. The experiment is conducted in a wind tunnel in the ranges of the real leatherback turtle's Reynolds number (Re) and angle of attack (α). The longitudinal ridges function differently according to the flow condition (i.e. Re and α). At low Re and negative α that represent the swimming condition of hatchlings and juveniles, the ridges significantly decrease the drag by generating streamwise vortices and delaying the main separation. On the other hand, at high Re and positive α that represent the swimming condition of adults, the ridges suppress the laminar separation bubble near the front part by generating streamwise vortices and enhance the lift and lift-to-drag ratio. Supported by the NRF program (2011-0028032).

  17. Lake trout spawning habitat in the Six Fathom Bank-Yankee Reef lake trout sanctuary, Lake Huron

    USGS Publications Warehouse

    Edsall, Thomas A.; Brown, Charles L.; Kennedy, Gregory W.; Poe, Thomas P.

    1992-01-01

    Attempts to reestablish self-sustaining stocks of lake trout (Salvelinus namaycush) in the lower four Great Lakes, where the species was extinguished in the 1950s and 1960s, have been largely unsuccessful. To avoid many of the problems believed to be contributing to this failure, the fishery management community recently established several sanctuaries in the offshore waters of the Great Lakes where the development and protection of self-sustaining stocks of lake trout would be a primary management objective. One of these, the Six Fathom Bank-Yankee Reef sanctuary, was created in the south-central portion of Lake Huron. This sanctuary covers 168,000 ha and includes the shallower portions of the Six Fathom and Ipperwash scarps, which are major bathymetric features in the southern half of the lake. Historical accounts describe Six Fathom Bank as the most important lake trout spawning ground in the lake. Here we present the results of lake bed surveys conducted in the sanctuary with side-scan sonar, underwater videocamera systems, and a small research submarine. Our observations of the lake bed are consistent with what is known of the bedrock stratigraphy, glacial history, and karst geomorphology of the Lake Huron basin. Most of the loose rock we found seemed to be derived from local carbonate bedrock formations, although non-carbonate rock probably from Precambrian sources to the north was also present in some areas. Much of the bedrock and loose rock displayed karst solution features described for the Bruce Peninsula on the Ontario shoreline. Our surveys revealed substantial areas of lake bed at water depths of 20–36 m that resembled suitable spawning and fry production habitat for the shallow-water strains of lake trout that are the focus of the rehabilitation effort. Low mid-lake nutrient levels documented recently by others and the extremely high abundance of Mysis relicta (an important item in the diet of young lake trout) that we documented on Yankee Reef

  18. Lake-level variability and water availability in the Great Lakes

    USGS Publications Warehouse

    Wilcox, Douglas A.; Thompson, Todd A.; Booth, Robert K.; Nicholas, J.R.

    2007-01-01

    In this report, we present recorded and reconstructed (pre-historical) changes in water levels in the Great Lakes, relate them to climate changes of the past, and highlight major water-availability implications for storage, coastal ecosystems, and human activities. 'Water availability,' as conceptualized herein, includes a recognition that water must be available for human and natural uses, but the balancing of how much should be set aside for which use is not discussed. The Great Lakes Basin covers a large area of North America. The lakes capture and store great volumes of water that are critical in maintaining human activities and natural ecosystems. Water enters the lakes mostly in the form of precipitation and streamflow. Although flow through the connecting channels is a primary output from the lakes, evaporation is also a major output. Water levels in the lakes vary naturally on timescales that range from hours to millennia; storage of water in the lakes changes at the seasonal to millennial scales in response to lake-level changes. Short-term changes result from storm surges and seiches and do not affect storage. Seasonal changes are driven by differences in net basin supply during the year related to snowmelt, precipitation, and evaporation. Annual to millennial changes are driven by subtle to major climatic changes affecting both precipitation (and resulting streamflow) and evaporation. Rebounding of the Earth's surface in response to loss of the weight of melted glaciers has differentially affected water levels. Rebound rates have not been uniform across the basin, causing the hydrologic outlet of each lake to rise in elevation more rapidly than some parts of the coastlines. The result is a long-term change in lake level with respect to shoreline features that differs from site to site. The reconstructed water-level history of Lake Michigan-Huron over the past 4,700 years shows three major high phases from 2,300 to 3,300, 1,100 to 2,000, and 0 to 800

  19. 76 FR 35909 - Temporary Concession Contract for Blue Ridge Parkway

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-06-20

    ... Concession Contract for Blue Ridge Parkway AGENCY: National Park Service, Interior. ACTION: Notice of proposed award of temporary concession contracts for Blue Ridge Parkway, NC/VA. SUMMARY: Pursuant to 36 CFR... concession contracts for the conduct of certain visitor services within the Blue Ridge Parkway, North...

  20. Microbial Life in Ridge Flank Crustal Fluids at Baby Bare Seamount, Juan de Fuca Ridge

    NASA Astrophysics Data System (ADS)

    Huber, J. A.; Johnson, H. P.; Butterfield, D. A.; Baross, J. A.

    2005-12-01

    To determine the microbial community diversity within old oceanic crust, a novel sampling strategy was used to collect crustal fluids at Baby Bare Seamount, a 3.5 Ma old outcrop located in the northeast Pacific Ocean on the eastern flank of the Juan de Fuca Ridge. Stainless steel probes were driven directly into the igneous ocean crust to obtain samples of ridge flank crustal fluids. Genetic signatures and enrichment cultures of microorganisms demonstrate that these crustal fluids host a microbial community composed of species indigenous to the subseafloor, including anaerobic thermophiles, and species from other deep-sea habitats, such as seawater and sediments. Evidence using molecular techniques indicates the presence of a relatively small but active microbial population, dominated by bacteria. The microbial community diversity found in the crustal fluids may indicate habitat variability in old oceanic crust, with inputs of nutrients from seawater, sediment pore-water fluids and possibly hydrothermal sources. This report further supports the presence of an indigenous microbial community in ridge flank crustal fluids and advances our understanding of the potential physiological and phylogenetic diversity of this community.

  1. Lake Life.

    ERIC Educational Resources Information Center

    Ohrn, Deborah Gore, Ed.

    1993-01-01

    This quarterly publication of the State Historical Society of Iowa features articles and activities for elementary school students. This summer issue focuses on the topic of lake life. The issue includes the following features: (1) "Where the Lakes Are Map"; (2) "Letter from the Lake"; (3) "Lake People"; (4)…

  2. Increased piscivory by lake whitefish in Lake Huron

    USGS Publications Warehouse

    Pothoven, Steven A.; Madenjian, Charles P.

    2013-01-01

    We evaluated the diet of Lake Whitefish Coregonus clupeaformis in Lake Huron during 2002–2011 to determine the importance of Round Goby Neogobius melanostomus and other fish as prey items. Lake Whitefish that had reached approximately 400 mm in length incorporated fish into their diets. The overall percentage of adult Lake Whitefish in Lake Huron that had eaten fish increased from 10% in 2002–2006 to 20% in 2007–2011, with a corresponding decrease in the frequency of Lake Whitefish that ate Dreissena spp. from 52% to 33%. During 2002–2006, Round Goby (wet mass, 38%), sculpins (Cottidae) (34%), and Ninespine Stickleback Pungitius pungitius (18%) were the primary fish eaten, whereas Round Goby accounted for 92% of the fish eaten in 2007–2011. Overall, Round Goby were found in the fewest Lake Whitefish stomachs in the north region of Lake Huron (6%) and in the most in the central (23%) and south (19%) regions of the lake. In the central region, Round Goby were eaten during all seasons that were sampled (spring through fall). In the south region, Round Goby were eaten only in the winter and spring but not in the summer when Dreissena spp. and spiny water flea Bythotrephes longimanus dominated the diet. Based on the 2007–2011 diet composition, an individual Lake Whitefish would need to have increased their consumption relative to that in 1983–1994 by 6% in the north region, 12% in the central region, and 41% in the southern region in order to achieve the same growth that was observed before dreissenid mussels arrived. However, Lake Whitefish weight adjusted for length only increased by 2% between 2002–2006 and 2007–2011 in the central region, decreased by 4% in the northern region, and remained constant in the southern region. This suggests that a shift toward more frequent piscivory does not necessarily improve the condition of a generalist feeder like Lake Whitefish.

  3. Wrinkle Ridges and Pit Craters

    NASA Image and Video Library

    2016-10-19

    Tectonic stresses highly modified this area of Ganges Catena, north of Valles Marineris. The long, skinny ridges (called "wrinkle ridges") are evidence of compressional stresses in Mars' crust that created a crack (fault) where one side was pushed on top of the other side, also known as a thrust fault. As shown by cross-cutting relationships, however, extensional stresses have more recently pulled the crust of Mars apart in this region. (HiRISE imaged this area in 2-by-2 binning mode, so a pixel represents a 50 x 50 square centimeter.) http://photojournal.jpl.nasa.gov/catalog/PIA21112

  4. Holocene lake-level fluctuations of Lake Aricota, Southern Peru

    USGS Publications Warehouse

    Placzek, C.; Quade, Jay; Betancourt, J.L.

    2001-01-01

    Lacustrine deposits exposed around Lake Aricota, Peru (17?? 22???S), a 7.5-km2 lake dammed by debris flows, provide a middle to late Holocene record of lake-level fluctuations. Chronological context for shoreline deposits was obtained from radiocarbon dating of vascular plant remains and other datable material with minimal 14C reservoir effects (<350 yr). Diatomites associated with highstands several meters above the modern lake level indicate wet episodes. Maximum Holocene lake level was attained before 6100 14C yr B.P. and ended ???2700 14C yr B.P. Moderately high lake levels occurred at 1700 and 1300 14C yr B.P. The highstand at Lake Aricota during the middle Holocene is coeval with a major lowstand at Lake Titicaca (16?? S), which is only 130 km to the northeast and shares a similar climatology. Comparisons with other marine and terrestrial records highlight emerging contradictions over the nature of mid-Holocene climate in the central Andes. ?? 2001 University of Washington.

  5. Holocene Lake-Level Fluctuations of Lake Aricota, Southern Peru

    NASA Astrophysics Data System (ADS)

    Placzek, Christa; Quade, Jay; Betancourt, Julio L.

    2001-09-01

    Lacustrine deposits exposed around Lake Aricota, Peru (17° 22‧S), a 7.5-km2 lake dammed by debris flows, provide a middle to late Holocene record of lake-level fluctuations. Chronological context for shoreline deposits was obtained from radiocarbon dating of vascular plant remains and other datable material with minimal 14C reservoir effects (<350 yr). Diatomites associated with highstands several meters above the modern lake level indicate wet episodes. Maximum Holocene lake level was attained before 6100 14C yr B.P. and ended ∼2700 14C yr B.P. Moderately high lake levels occurred at 1700 and 1300 14C yr B.P. The highstand at Lake Aricota during the middle Holocene is coeval with a major lowstand at Lake Titicaca (16°S), which is only 130 km to the northeast and shares a similar climatology. Comparisons with other marine and terrestrial records highlight emerging contradictions over the nature of mid-Holocene climate in the central Andes.

  6. Reevaluation of lake trout and lake whitefish bioenergetics models

    USGS Publications Warehouse

    Madenjian, Charles P.; Pothoven, Steve A.; Kao, Yu-Chun

    2013-01-01

    Using a corrected algorithm for balancing the energy budget, we reevaluated the Wisconsin bioenergetics model for lake trout (Salvelinus namaycush) in the laboratory and for lake whitefish (Coregonus clupeaformis) in the laboratory and in the field. For lake trout, results showed that the bioenergetics model slightly overestimated food consumption by the lake trout when they were fed low and intermediate rations, whereas the model predicted food consumption by lake trout fed ad libitum without any detectable bias. The slight bias in model predictions for lake trout on restricted rations may have been an artifact of the feeding schedule for these fish, and we would therefore recommend application of the Wisconsin lake trout bioenergetics model to lake trout populations in the field without any revisions to the model. Use of the Wisconsin bioenergetics model for coregonids resulted in overestimation of food consumption by lake whitefish both in the laboratory and in the field by between 20 and 30%, on average. This overestimation of food consumption was most likely due to overestimation of respiration rate. We therefore adjusted the respiration component of the bioenergetics model to obtain a good fit to the observed consumption in our laboratory tanks. The adjusted model predicted the consumption in the laboratory and the field without any detectable bias. Until a detailed lake whitefish respiration study can be conducted, we recommend application of our adjusted version of the Wisconsin generalized coregonid bioenergetics model to lake whitefish populations in the field.

  7. Mantle Convection beneath the Aegir Ridge, a Shadow in the Iceland Hotspot

    NASA Astrophysics Data System (ADS)

    Howell, S. M.; Ito, G.; Breivik, A. J.; Hanan, B. B.; Mjelde, R.; Sayit, K.; Vogt, P. R.

    2012-12-01

    The Iceland Hotspot has produced extensive volcanism spanning much of the ocean basin between Greenland and Norway, forming one of the world's largest igneous provinces. However, an apparent igneous "shadow" in hotspot activity is located at the fossil Aegir Ridge, which formed anomalously thin crust, despite this ridge being near the Iceland hotspot when it was active. The Aegir Ridge accommodated seafloor spreading northeast of present-day Iceland from the time of continental breakup at ~55 Ma until ~25 Ma, at which point spreading shifted west to the Kolbeinsey Ridge. To address the cause of the anomalously thin crust produced by the Aegir Ridge, we use three-dimensional numerical models to simulate the interaction between a mantle plume beneath the Iceland hotspot, rifting continental lithosphere, and the time-evolving North Atlantic ridge system. Two end-member hypotheses were investigated: (1) Material emanating from the Iceland mantle plume was blocked from reaching the Aegir Ridge by the thick lithosphere of the Jan Mayen Microcontinent as the Kolbeinsey Ridge began rifting it from Greenland at ~30 Ma, just east of the plume center; (2) Plume material was not blocked and did reach the Aegir Ridge, but had already experienced partial melting closer to the hotspot. This material was then unable to produce melt volumes at the Aegir Ridge comparable to those of pristine mantle. To test these hypotheses, we vary the volume flux and viscosity of the plume, and identify which conditions do and do not lead to the Aegir Ridge forming anomalously thin crust. Results show that the combination of plume material being drawn into the lithospheric channels beneath the Reykjanes Ridge and Kolbeinsey Ridge after their respective openings, and the impedance of plume flow by the Jan Mayen Microcontinent (hypothesis 1), can deprive the Aegir Ridge of plume influence. This leads to low crustal thicknesses that are comparable to those observed. We have yet to produce a model

  8. Cedar Ridge Camp: Using the Local Environment

    ERIC Educational Resources Information Center

    Burke, Grayson

    2007-01-01

    In 2007 Cedar Ridge Camp opened for its first season as a traditional co-ed summer camp and year-round outdoor education and recreation centre. The mission would centre on creating a program that would encourage personal development and growth through a shared outdoor experience. Cedar Ridge's main goals were to promote the formation of close…

  9. Tectonics of ridge-transform intersections at the Kane fracture zone

    NASA Astrophysics Data System (ADS)

    Karson, J. A.; Dick, H. J. B.

    1983-03-01

    The Kane Transform offsets spreading-center segments of the Mid-Atlantic Ridge by about 150 km at 24° N latitude. In terms of its first-order morphological, geological, and geophysical characteristics it appears to be typical of long-offset (>100 km), slow-slipping (2 cm yr-1) ridge-ridge transform faults. High-resolution geological observations were made from deep-towed ANGUS photographs and the manned submersible ALVIN at the ridge-transform intersections and indicate similar relationships in these two regions. These data indicate that over a distance of about 20 km as the spreading axes approach the fracture zone, the two flanks of each ridge axis behave in very different ways. Along the flanks that intersect the active transform zone the rift valley floor deepens and the surface expression of volcanism becomes increasingly narrow and eventually absent at the intersection where only a sediment-covered ‘nodal basin’ exists. The adjacent median valley walls have structural trends that are oblique to both the ridge and the transform and have as much as 4 km of relief. These are tectonically active regions that have only a thin (<200 m), highly fractured, and discontinuous carapace of volcanic rocks overlying a variably deformed and metamorphosed assemblage of gabbroic rocks. Overprinting relationships reveal a complex history of crustal extension and rapid vertical uplift. In contrast, the opposing flanks of the ridge axes, that intersect the non-transform zones appear to be similar in many respects to those examined elsewhere along slow-spreading ridges. In general, a near-axial horst and graben terrain floored by relatively young volcanics passes laterally into median valley walls with a simple block-faulted character where only volcanic rocks have been found. Along strike toward the fracture zone, the youngest volcanics form linear constructional volcanic ridges that transect the entire width of the fracture zone valley. These volcanics are continuous with

  10. Calendar year 1996 annual groundwater monitoring report for the Chestnut Ridge Hydrogeologic Regime at the U.S. Department of Energy Y-12 Plant, Oak Ridge, Tennessee

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    NONE

    1997-02-01

    This annual monitoring report contains groundwater and surface water monitoring data obtained in the Chestnut Ridge Hydrogeologic Regime (Chestnut Ridge Regime) during calendar year (CY) 1996. The Chestnut Ridge Regime encompasses a section of Chestnut Ridge west of Scarboro Road and east of an unnamed drainage feature southwest of the US Department of Energy (DOE) Oak Ridge Y-12 Plant (unless otherwise noted, directions are in reference to the Y-12 Plant administrative grid). The Chestnut Ridge Regime contains several sites used for management of hazardous and nonhazardous wastes associated with plant operations. Groundwater and surface water quality monitoring associated with thesemore » waste management sites is performed under the auspices of the Y-12 Plant Groundwater Protection Program (GWPP). Included in this annual monitoring report are the groundwater monitoring data obtained in compliance with the Resource Conservation and Recovery Act (RCRA) Post-Closure Permit for the Chestnut Ridge Regime (post-closure permit) issued by the Tennessee Department of Environment and Conservation (TDEC) in June 1996. Besides the signed certification statement and the RCRA facility information summarized below, condition II.C.6 of the post-closure permit requires annual reporting of groundwater monitoring activities, inclusive of the analytical data and results of applicable data evaluations, performed at three RCRA hazardous waste treatment, storage, or disposal (TSD) units: the Chestnut Ridge Sediment Disposal Basin (Sediment Disposal Basin), the Chestnut Ridge Security Pits (Security Pits), and Kerr Hollow Quarry.« less

  11. Brief description as of April, 1968, of the geology and hydrology of the Lake Minnequa area, Pueblo, Colorado, and suggested solutions for trouble caused by a high water table

    USGS Publications Warehouse

    Scott, Glenn R.

    1972-01-01

    Lake Minnequa lies in a poorly drained broad upland buried valley west of the valley of Salt Creek. Immediately north of Lake Minnequa the buried valley is sharply constricted in sees. 11 and 12, T. 21 S., R. 65 W., where it is entrenched in a buried ridge of bedrock (see geologic map).  The bedrock throughout the buried valley is composed of calcareous shale, limestone, and chalk of the Smoky Hill Shale Member of the Niobrara Formation.  These beds are relatively impermeable to the flow of ground water, but contribute large quantities of sodium sulfate to both the surface and ground water.

  12. Late Holocene lake-level fluctuations in Walker Lake, Nevada, USA

    USGS Publications Warehouse

    Yuan, F.; Linsley, B.K.; Howe, S.S.; Lund, S.P.; McGeehin, J.P.

    2006-01-01

    Walker Lake, a hydrologically closed, saline, and alkaline lake, is situated along the western margin of the Great Basin in Nevada of the western United States. Analyses of the magnetic susceptibility (??), total inorganic carbon (TIC), and oxygen isotopic composition (??18O) of carbonate sediments including ostracode shells (Limnocythere ceriotuberosa) from Walker Lake allow us to extend the sediment record of lake-level fluctuations back to 2700??years B.P. There are approximately five major stages over the course of the late Holocene hydrologic evolution in Walker Lake: an early lowstand (> 2400??years B.P.), a lake-filling period (??? 2400 to ??? 1000??years B.P.), a lake-level lowering period during the Medieval Warm Period (MWP) (??? 1000 to ??? 600??years B.P.), a relatively wet period (??? 600 to ??? 100??years B.P.), and the anthropogenically induced lake-level lowering period (< 100??years B.P.). The most pronounced lowstand of Walker Lake occurred at ??? 2400??years B.P., as indicated by the relatively high values of ??18O. This is generally in agreement with the previous lower resolution paleoclimate results from Walker Lake, but contrasts with the sediment records from adjacent Pyramid Lake and Siesta Lake. The pronounced lowstand suggests that the Walker River that fills Walker Lake may have partially diverted into the Carson Sink through the Adrian paleochannel between 2700 to 1400??years B.P. ?? 2006 Elsevier B.V. All rights reserved.

  13. Calculation of area and volume for the south part of Great Salt Lake, Utah

    USGS Publications Warehouse

    Baskin, Robert L.

    2005-01-01

    The U.S. Geological Survey, in cooperation with the Utah Department of Natural Resources, Division of Wildlife Resources, collected bathymetric data for the south part of Great Salt Lake during 2002-04 using a single-beam, high-definition fathometer and real-time differential global positioning system. About 7.6 million depth measurements were collected along more than 930 miles (1,690 kilometers) of survey transects. Sound-velocity profiles were obtained in conjunction with the bathymetric data to provide time-of-travel corrections to the depth calculations. Data were processed with commercial hydrographic software and exported into geographic information system (GIS) software for mapping and calculation of area and volume. Area and volume calculations show a maximum area of about 508,000 acres (2,056 square kilometers) and a maximum volume of about 9,257,000 acre-feet (11.42 cubic kilometers) at a water-surface altitude of 4,200 feet (1,280 meters). Minimum water-surface altitude of the south part of Great Salt Lake is just below 4,167 feet (1,279 meters) in the area just south of the Union Pacific railroad causeway halfway between Promontory Point and the western edge of the lake. At this altitude, and continuing up to about 4,176 feet (1,279 meters), the south part of the lake is separated into two areas by a ridge extending from Promontory Point to Hat Island. Calculations for area and volume are based on a low altitude of 4,167 feet (1,279 meters) to a high altitude of 4,200 feet (1,280 meters).

  14. A 600,000 year long continental pollen record from Lake Van, eastern Turkey

    NASA Astrophysics Data System (ADS)

    Litt, T.; Pickarski, N.; Heumann, G.

    2014-12-01

    Lake Van is the fourth largest terminal lake in the world (38.5°N, 43 °E, volume 607 km3, area 3570 km2, maximum water depth 460 m), extending for 130 km WSW-ENE on the Eastern Anatolian High Plateau, Turkey. The sedimentary record of Lake Van, partly laminated, obtains a long and continuous continental sequence that covers multiple interglacial-glacial cycles. Promoted by the potential of the sedimentary sequence for reconstructing the paleoecological and paleoclimate development of the Near East, a deep drilling operation was carried out in 2010 supported by the International Continental Scientific Drilling Program (ICDP). The 119 m long continental record is based on a well-dated composite profile drilled on the so-called Ahlat Ridge in water depth of 360 m encompassing the last 600,000 years. It contains the longest continuous continental pollen record of the Quaternary in the entire Near East and central Asia obtained to date. It documents glacial and interglacial stages as well as pronounced interstadials encompassing the entire 600 ka of the sedimentary record. The cold-adapted vegetation in the Lake Van region during glacial stages and stadial substages can be described as dwarf-shrub steppe and desert steppe very similar to each other. The climax vegetation of the interglacial stages in the Lake Van region is characterized by an oak steppe-forest with pistachio and juniper. It is interesting to note that, in contrast to the atmospheric CO2 concentration from Antarctic ice cores or marine isotope values based on benthic foraminifera, there is no clear subdivision in the Lake Van pollen record between low-amplitude interglacials (cooler cycles) prior the mid-Brunhes event (MBE) at 430 ka and high-amplitude, post MBE interglacials. Lower CO2 concentrations in the atmosphere might be compensated by stronger insolation forcing during Marine Isotope Stages (MIS) 13a and 15a. A similar pattern can be observed during the triplicate interglacial complex MIS 7

  15. Coupled ridge waveguide distributed feedback quantum cascade laser arrays

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Liu, Ying-Hui; Zhang, Jin-Chuan, E-mail: zhangjinchuan@semi.ac.cn; Yan, Fang-Liang

    2015-04-06

    A coupled ridge waveguide quantum cascade laser (QCL) array consisting of fifteen elements with parallel integration was presented. In-phase fundamental mode operation in each element is secured by both the index-guided nature of the ridge and delicate loss management by properly designed geometries of the ridges and interspaces. Single-lobe lateral far-field with a nearly diffraction limited beam pattern was obtained. By incorporating a one-dimensional buried distributed feedback grating, the in-phase-operating coupled ridge waveguide QCL design provides an efficient solution to obtaining high output power and stable single longitudinal mode emission. The simplicity of this structure and fabrication process makes thismore » approach attractive to many practical applications.« less

  16. Wrinkle ridges, stress domains, and kinematics of venusian plains

    NASA Technical Reports Server (NTRS)

    Mcgill, George E.

    1993-01-01

    Wrinkle ridges are nearly ubiquitous landforms on the plains of Venus. By analogy with similar structures on other planets, venusian wrinkle ridges are inferred to trend normal to the direction of maximum principal compression in the crust, an inference that is verified by geometrical relationships with positive and negative relief features on Venus. Because plains are the dominant terrain on Venus, wrinkle ridges provide an excellent opportunity to determine the orientations of shallow crustal principal stress trajectories over most of the planet. In most places there are two or more sets of wrinkle ridges, and commonly one of these persists over a large area, defining a regional stress domain. Intersection relationships indicate that these domains differ in age.

  17. Bathythermal habitat use by strains of Great Lakes- and Finger Lakes-origin lake trout in Lake Huron after a change in prey fish abundance and composition

    USGS Publications Warehouse

    Bergstedt, Roger A.; Argyle, Ray L.; Krueger, Charles C.; Taylor, William W.

    2012-01-01

    A study conducted in Lake Huron during October 1998–June 2001 found that strains of Great Lakes-origin (GLO) lake trout Salvelinus namaycush occupied significantly higher temperatures than did Finger Lakes-origin (FLO; New York) lake trout based on data from archival (or data storage) telemetry tags that recorded only temperature. During 2002 and 2003, we implanted archival tags that recorded depth as well as temperature in GLO and FLO lake trout in Lake Huron. Data subsequently recorded by those tags spanned 2002–2005. Based on those data, we examined whether temperatures and depths occupied by GLO and FLO lake trout differed during 2002–2005. Temperatures occupied during those years were also compared with occupied temperatures reported for 1998–2001, before a substantial decline in prey fish biomass. Temperatures occupied by GLO lake trout were again significantly higher than those occupied by FLO lake trout. This result supports the conclusion of the previous study. The GLO lake trout also occupied significantly shallower depths than FLO lake trout. In 2002–2005, both GLO and FLO lake trout occupied significantly lower temperatures than they did in 1998–2001. Aside from the sharp decline in prey fish biomass between study periods, the formerly abundant pelagic alewife Alosa pseudoharengus virtually disappeared and the demersal round goby Neogobius melanostomus invaded the lake and became locally abundant. The lower temperatures occupied by lake trout in Lake Huron during 2002–2005 may be attributable to changes in the composition of the prey fish community, food scarcity (i.e., a retreat to cooler water could increase conversion efficiency), or both.

  18. Chemours Pompton Lakes Works Site, Pompton Lakes, NJ

    EPA Pesticide Factsheets

    E.I. DuPont De Nemours & Company is located at 2000 Cannonball Road, Pompton Lakes, New Jersey. The DuPont Pompton Lakes Works site (DuPont) occupies approximately 570 acres of land in Pompton Lakes and Wanaque.

  19. Europan double ridge morphometry as a test of formation models

    NASA Astrophysics Data System (ADS)

    Dameron, Ashley C.; Burr, Devon M.

    2018-05-01

    Double ridges on the Jovian satellite Europa consist of two parallel ridges with a central trough. Although these features are nearly ubiquitous on Europa, their formation mechanism(s) is (are) not yet well-understood. Previous hypotheses for their formation can be divided into two groups based on 1) the expected interior slope angles and 2) the magnitude of interior/exterior slope symmetry. The published hypotheses in the first ("fracture") group entail brittle deformation of the crust, either by diapirism, shear heating, or buckling due to compression. Because these mechanisms imply uplift of near-vertical fractures, their predicted interior slopes are steeper than the angle of repose (AOR) with shallower exterior slopes. The second ("flow") group includes cryosedimentary and cryovolcanic processes - explosive or effusive cryovolcanism and tidal squeezing -, which are predicted to form ridge slopes at or below the AOR. Explosive cryovolcanism would form self-symmetric ridges, whereas effusive cryolavas and cryo-sediments deposited during tidal squeezing would likely not exhibit slope symmetry. To distinguish between these two groups of hypothesized formation mechanisms, we derived measurements of interior slope angle and interior/exterior slope symmetry at multiple locations on Europa through analysis of data from the Galileo Solid State Imaging (SSI) camera. Two types of data were used: i) elevation data from five stereo-pair digital elevation models (DEMs) covering four ridges (580 individual measurements), and ii) ridge shadow length measurements taken on individual images over 40 ridges (200 individual measurements). Our results shows that slopes measured on our DEMs, located in the Cilix and Banded Plains regions, typically fall below the AOR, and slope symmetry is dominant. Two different shadow measurement techniques implemented to calculate interior slopes yielded slope angles that also fall below the AOR. The shallow interior slopes derived from both

  20. Porewater salinity reveals past lake-level changes in Lake Van, the Earth's largest soda lake.

    PubMed

    Tomonaga, Yama; Brennwald, Matthias S; Livingstone, David M; Kwiecien, Olga; Randlett, Marie-Ève; Stockhecke, Mona; Unwin, Katie; Anselmetti, Flavio S; Beer, Jürg; Haug, Gerald H; Schubert, Carsten J; Sturm, Mike; Kipfer, Rolf

    2017-03-22

    In closed-basin lakes, sediment porewater salinity can potentially be used as a conservative tracer to reconstruct past fluctuations in lake level. However, until now, porewater salinity profiles did not allow quantitative estimates of past lake-level changes because, in contrast to the oceans, significant salinity changes (e.g., local concentration minima and maxima) had never been observed in lacustrine sediments. Here we show that the salinity measured in the sediment pore water of Lake Van (Turkey) allows straightforward reconstruction of two major transgressions and a major regression that occurred during the last 250 ka. We observed strong changes in the vertical salinity profiles of the pore water of the uppermost 100 m of the sediments in Lake Van. As the salinity balance of Lake Van is almost at steady-state, these salinity changes indicate major lake-level changes in the past. In line with previous studies on lake terraces and with seismic and sedimentological surveys, we identify two major transgressions of up to +105 m with respect to the current lake level at about 135 ka BP and 248 ka BP starting at the onset of the two previous interglacials (MIS5e and MIS7), and a major regression of about -200 m at about 30 ka BP during the last ice age.

  1. The Mid-Ocean Ridge.

    ERIC Educational Resources Information Center

    Macdonald, Kenneth C.; Fox, Paul J.

    1990-01-01

    Described are concepts involved with the formation and actions of the Mid-Ocean Ridge. Sea-floor spreading, the magma supply model, discontinuities, off-axis structures, overlaps and deviation, and aquatic life are discussed. (CW)

  2. Spatial and temporal genetic diversity of lake whitefish (Coregonus clupeaformis (Mitchill)) from Lake Huron and Lake Erie

    USGS Publications Warehouse

    Stott, Wendylee; Ebener, Mark P.; Mohr, Lloyd; Hartman, Travis; Johnson, Jim; Roseman, Edward F.

    2013-01-01

    Lake whitefish (Coregonus clupeaformis (Mitchill)) are important commercially, culturally, and ecologically in the Laurentian Great Lakes. Stocks of lake whitefish in the Great Lakes have recovered from low levels of abundance in the 1960s. Reductions in abundance, loss of habitat and environmental degradation can be accompanied by losses of genetic diversity and overall fitness that may persist even as populations recover demographically. Therefore, it is important to be able to identify stocks that have reduced levels of genetic diversity. In this study, we investigated patterns of genetic diversity at microsatellite DNA loci in lake whitefish collected between 1927 and 1929 (historical period) and between 1997 and 2005 (contemporary period) from Lake Huron and Lake Erie. Genetic analysis of lake whitefish from Lakes Huron and Erie shows that the amount of population structuring varies from lake to lake. Greater genetic divergences among collections from Lake Huron may be the result of sampling scale, migration patterns and demographic processes. Fluctuations in abundance of lake whitefish populations may have resulted in periods of increased genetic drift that have resulted in changes in allele frequencies over time, but periodic genetic drift was not severe enough to result in a significant loss of genetic diversity. Migration among stocks may have decreased levels of genetic differentiation while not completely obscuring stock boundaries. Recent changes in spatial boundaries to stocks, the number of stocks and life history characteristics of stocks further demonstrate the potential of coregonids for a swift and varied response to environmental change and emphasise the importance of incorporating both spatial and temporal considerations into management plans to ensure that diversity is preserved.

  3. Geomorphology of the Chippewa River delta of Glacial Lake Saginaw, central Lower Michigan, USA

    NASA Astrophysics Data System (ADS)

    Connallon, Christopher B.; Schaetzl, Randall J.

    2017-08-01

    We introduce, characterize, and interpret the geomorphic history of a relict, Pleistocene-aged delta of the Chippewa River in central Lower Michigan. The broad, sandy Chippewa delta developed into various stages of Glacial Lake Saginaw, between ca. ≈ 17 and 15 ka·BP (calibrated ages). Although the delta was first identified in 1955 on a statewide glacial geology map, neither its extent nor its Pleistocene history had been previously determined. The delta is typically forested, owing to its wet, sandy soils, which stand out against the agricultural fields of the surrounding, loamy lake plain sediments. The delta heads near the city of Mt Pleasant and extends eastward onto the Saginaw Lowlands, i.e., the plain of Glacial Lake Saginaw. Data from 3285 water well logs, 180 hand augered sites, and 185 points randomly located in a GIS on two-storied (sand over loam) soils were used to determine the extent, textural properties, and thickness of the delta. The delta is ≈ 18 km wide and ≈ 38 km long and is sandy throughout. Deltaic sediments from neighboring rivers that also drained into Glacial Lake Saginaw merge with the lower Chippewa delta, obscuring its boundary there. The delta is thickest near the delta's head and in the center, but thins to 1-2 m or less on its eastern margins. Mean thicknesses are 2.3-2.9 m, suggestive of a thin sediment body, frequently impacted by the waves and fluctuating waters of the lakes. Although beach ridges are only weakly expressed across the delta because of the sandy sediment, the coarsest parts of the delta are generally coincident with some of these inferred former shorezones and have a broad, incised channel that formed while lake levels were low. The thick upper delta generally lies above the relict shorelines of Glacial Lakes Saginaw and Arkona (≈ 17.1 to ≈ 16 ka·BP), whereas most of the thin, distal delta is associated with Glacial Lake Warren (≈ 15 ka·BP). Together, these data suggest that the Chippewa delta formed

  4. Banded Ridges in Hellas

    NASA Image and Video Library

    2014-01-09

    Low lying areas in the Hellas region, which is the largest impact basin on Mars, often show complex groups of banded ridges, furrows, and pits as seen in this observation from NASA Mars Reconnaissance Orbiter.

  5. Structure and origin of the J Anomaly Ridge, western North Atlantic Ocean

    NASA Astrophysics Data System (ADS)

    Tucholke, Brian E.; Ludwig, William J.

    1982-11-01

    The J Anomaly Ridge is a structural ridge or step in oceanic basement that extends southwest from the eastern end of the Grand Banks. It lies beneath the J magnetic anomaly at the young end (M-4 to M-0) of the M series magnetic anomalies. Its structural counterpart beneath the J anomaly in the eastern Atlantic is the Madeira-Tore Rise, but this feature has been overprinted by post-middle Cretaceous deformation and volcanism. In order to study the origin and evolution of the J Anomaly Ridge-Madeira-Tore Rise system, we obtained seismic refraction and multichannel reflection profiles across the J Anomaly Ridge near 39°N latitude. The western ridge flank consists of a series of crustal blocks downdropped along west-dipping normal faults, but the eastern slope to younger crust is gentle and relatively unfaulted. The western flank also is subparallel to seafloor isochrons, becoming younger to the south. Anomalously smooth basement caps the ridge crest, and it locally exhibits internal, eastward-dipping reflectors similar in configuration to those within subaerially emplaced basalt flows on Iceland. When isostatically corrected for sediment load, the northern part of the J Anomaly Ridge has basement depths about 1400 m shallower than in our study area, and deep sea drilling has shown that the northern ridge was subaerially exposed during the middle Cretaceous. We suggest that most of the system originated under subaerial conditions at the time of late-stage rifting between the adjacent Grand Banks and Iberia. The excess magma required to form the ridge may have been vented from a mantle plume beneath the Grand Banks-Iberia rift zone and channelled southward beneath the rift axis of the abutting Mid-Atlantic Ridge. Resulting edifice-building volcanism constructed the ridge system between anomalies M-4 and M-0, moving southward along the ridge axis at about 50 mm/yr. About M-0 time, when true drift began between Iberia and the Grand Banks, this southward venting rapidly

  6. The Central Symmetry Analysis of Wrinkle Ridges in Lunar Mare Serenitatis

    NASA Astrophysics Data System (ADS)

    Yao, Meijuan; Chen, Jianping

    2018-03-01

    Wrinkle ridges are one of the most common structures usually found in lunar mare basalts, and their formations are closely related to the lunar mare. In this paper, wrinkle ridges in Mare Serenitatis were identified and mapped via high-resolution data acquired from SELENE, and a quantitative method was introduced to analyze the degree of central symmetry of the wrinkle ridges distributed in a concentric or radial pattern. Meanwhile, two methods were used to measure the lengths and orientations of wrinkle ridges before calculating their central symmetry value. Based on the mapped wrinkle ridges, we calculated the central symmetry value of the wrinkle ridges for the whole Mare Serenitatis as well as for the four circular ridge systems proposed by a previous study via this method. We also analyzed the factors that would cause discrepancies when calculating the central symmetry value. The results indicate that the method can be used to quantitatively analyze the degree of central symmetry of the linear features that were concentrically or radially oriented and can reflect the stress field characteristics.

  7. Movements of hatchery-reared lake trout in Lake Superior

    USGS Publications Warehouse

    Pycha, Richard L.; Dryer, William R.; King, George R.

    1965-01-01

    The history of stocking of lake trout (Salvelinus namaycush) in the Great Lakes is reviewed. The study of movements is based on capture of 24,275 fin-clipped lake trout taken in experimental gill nets and trawls and commercial gill nets. Yearling lake trout planted from shore dispersed to 15-fath (27-m) depths in 3A? hr. Most fish remained within 2 miles (3.2 km) of the planting site 2 months, but within 4 months some fish had moved as much as 17 miles (27 km). The highest abundance of planted lake trout was in areas 2-4 miles (3.2-6.4 km) from the planting site even 3 years after release. Distance moved and size of fish were not correlated. Dispersal of lake trout begins at planting and probably continues until the fish are mature. Most movement was eastward in southern Lake Superior and followed the counterclockwise surface currents. Movement is most rapid in areas of strong currents and slowest in areas of weak currents or eddies. Movement to areas west of the Keweenaw Peninsula was insignificant from plantings in Keweenaw Bay and nil from other plantings farther east. Lake trout planted in the eastern third of the lake dispersed more randomly than those planted farther west. Few fish moved farther offshore than the 50-fath (91-m) contour. Lake trout planted in Canadian waters made insignificant contributions to populations in US waters.

  8. Maxillary anterior ridge augmentation with recombinant human bone morphogenetic protein 2.

    PubMed

    Edmunds, Ryan K; Mealey, Brian L; Mills, Michael P; Thoma, Daniel S; Schoolfield, John; Cochran, David L; Mellonig, Jim

    2014-01-01

    No human studies exist on the use of recombinant human bone morphogenetic protein 2 (rhBMP-2) on an absorbable collagen sponge (ACS) as a sole graft material for lateral ridge augmentation in large ridge defect sites. This series evaluates the treatment outcome of maxillary anterior lateral ridge augmentation with rhBMP-2/ACS. Twenty patients were treated with rhBMP-2/ACS and fixation screws for space maintenance. Cone beam volumetric tomography measurements were used to determine gain in ridge width, and a bone core biopsy was obtained. The mean horizontal ridge gain was 1.2 mm across sites, and every site gained width.

  9. Unfaulting the Sardarapat Ridge, Southwest Armenia

    NASA Astrophysics Data System (ADS)

    Wetmore, P.; Connor, C.; Connor, L. J.; Savov, I. P.; Karakhanyan, A.

    2012-12-01

    Armenia is located near the core of contractional deformation associated with the collision between the Arabian and Eurasian tectonic plates. Several studies of this region, including portions of adjacent Georgia, Iran, and Turkey, have indicated that 1-2 mm/yr of intra-plate, north-south shortening is primarily accommodated by a network of E-W trending thrust faults, and NW-trending (dextral) and NE-trending (sinistral) strike-slip faults. One proposed fault in this network, the Sardarapat Fault (SF), was investigated as part of a regional seismic hazard assessment ahead of the installation of a replacement reactor at the Armenian Nuclear Power Plant (ANPP). The SF is primarily defined by the Sardarapat Ridge (SR), which is a WNW-trending, 40-70 m high topographic feature located just north of the Arax River and the Turkey-Armenia border. The stratigraphy comprising this ridge includes alluvium overlying several meters of lacustrine deposits above a crystal-rich basaltic lava flow that yields an Ar-Ar age of 0.9 +/- 0.02 Ma. The alluvial sediments on the ridge contain early Bronze age (3832-3470 BP) artifacts at an elevation 25 m above those of the surrounding alluvial plane. This has lead to the suggestion that the SR is bound to the south (the steepest side) by the SF, which is uplifting the ridge at a rate of 0.7 mm/yr. However, despite the prominence and trend of the ridge there are no unequivocal observations, such as scarps or exposures of fault rocks, to support the existence of the SF. The goal of the investigation of the SR area was to test various models for the formation of the ridge including faulting and combined volcanic and erosional processes. We therefore collected gravimetric, magnetic, magneto-tellurics (MT), and transient electromagnetic (TEM) data across an area of ~400 km2, and used correlations of stratigraphic data from coreholes drilled proximal to the study area to define the geometry of the contact between the basement and basin fill to

  10. The Statherian itabirite-bearing sequence from the Morro Escuro Ridge, Santa Maria de Itabira, Minas Gerais, Brazil

    NASA Astrophysics Data System (ADS)

    Silveira Braga, Flávia Cristina; Rosière, Carlos Alberto; Queiroga, Gláucia Nascimento; Rolim, Vassily Khoury; Santos, João Orestes Schneider; McNaughton, Neal Jesse

    2015-03-01

    The itabirite-bearing metasedimentary sequence from Morro Escuro Ridge comprises the basal units of the Espinhaço Supergroup and makes up a small tectonic inlier developed during one of the Brasiliano orogenic events (800-500 Ma), amongst horses of the Archean TTG gneisses, including sheared granites of the anorogenic Borrachudos Suite (˜1700 Ma). The metasedimentary rocks are comprised of low-to intermediate-amphibolite facies schists, quartzites, conglomerates and banded iron formation (itabirite) correlatable with the sequences of the Serro Group, which underlies the metasedimentary rocks of the Espinhaço Supergroup in the Serra da Serpentina Ridge. A maximum Statherian deposition age (1668 Ma) was established using SHRIMP U-Pb isotopic constraints on zircon grains from conglomerate and quartzite units overlying the itabirite. The itabirite is predominantly hematitic and its geochemical characteristics are typical of a Lake Superior-type BIF deposited in a platformal, suboxic to anoxic environment distant from Fe-bearing hydrothermal vents. Close to the contact zone with amphibolites of the Early Neoproterozoic Pedro Lessa mafic suite, an increase of the magnetite content and crystallization of metasomatic Mg-hornblende and Ce-allanite can be observed. These mineralogical changes developed preferentially along the igneous contact zone but are probably co-genetic with the formation of alteration haloes in zircon grains during the Neoproterozoic Brasiliano orogeny (506 ± 6 Ma).

  11. Ridges on Europa: Origin by Incremental Ice-Wedging

    NASA Technical Reports Server (NTRS)

    Melosh, H. J.; Turtle, E. P.

    2004-01-01

    The surface of Europa is covered by ridges that display a variety of morphologies . The most common type is characterized by a double ridge divided by an axial trough. These ridges are, in general, narrow (typically only a few km across) and remarkably linear. They are up to a few hundred meters high and the inner and outer slopes appear to stand at the angle of repose . A number of diverse mechanisms have been proposed to explain the formation of these ubiquitous features , although none can fully account for all of their observed characteristics. We propose a different formation theory in which accumulation of material within cracks that open during the extensional phase of the tidal cycle prevents complete closure of the cracks during the tidal cycle s compressional phase. This accumulation deforms the surrounding ice and, in time, results in the growth of a landform remarkably similar to the ridges observed on Europa.

  12. Energy density of lake whitefish Coregonus clupeaformis in Lakes Huron and Michigan

    USGS Publications Warehouse

    Pothoven, S.A.; Nalepa, T.F.; Madenjian, C.P.; Rediske, R.R.; Schneeberger, P.J.; He, J.X.

    2006-01-01

    We collected lake whitefish Coregonus clupeaformis off Alpena and Tawas City, Michigan, USA in Lake Huron and off Muskegon, Michigan USA in Lake Michigan during 2002–2004. We determined energy density and percent dry weight for lake whitefish from both lakes and lipid content for Lake Michigan fish. Energy density increased with increasing fish weight up to 800 g, and then remained relatively constant with further increases in fish weight. Energy density, adjusted for weight, was lower in Lake Huron than in Lake Michigan for both small (≤800 g) and large fish (>800 g). Energy density did not differ seasonally for small or large lake whitefish or between adult male and female fish. Energy density was strongly correlated with percent dry weight and percent lipid content. Based on data from commercially caught lake whitefish, body condition was lower in Lake Huron than Lake Michigan during 1981–2003, indicating that the dissimilarity in body condition between the lakes could be long standing. Energy density and lipid content in 2002–2004 in Lake Michigan were lower than data for comparable sized fish collected in 1969–1971. Differences in energy density between lakes were attributed to variation in diet and prey energy content as well as factors that affect feeding rates such as lake whitefish density and prey abundance.

  13. Martian Ridge Looming Above Curiosity Prior to Ascent

    NASA Image and Video Library

    2017-09-13

    Researchers used the Mast Camera (Mastcam) on NASA's Curiosity Mars rover to gain this detailed view of layers in "Vera Rubin Ridge" from just below the ridge. The scene combines 70 images taken with the Mastcam's right-eye, telephoto-lens camera, on Aug. 13, 2017, during the 1,785th Martian day, or sol, of Curiosity's work on Mars. This and other Mastcam panoramas show details of the sedimentary rocks that make up the "Vera Rubin Ridge." This distinct topographic feature located on the lower slopes of Mount Sharp (Aeolis Mons) is characterized by the presence of hematite, an iron-oxide mineral, which has been detected from orbit. The Mastcam images show that the rocks making up the lower part of the ridge are characterized by distinct horizontal stratification with individual rock layers of the order of several inches (tens of centimeters) thick. Scientists on the mission are using such images to determine the ancient environment these rocks were deposited in. The repeated beds indicate progressive accumulation of sediments that now make up the lower part of Mount Sharp, although from this distance it is not possible to know if they were formed by aqueous or wind-blown processes. Close-up images collected as the rover climbs the ridge will help answer this question. The stratified rocks are cross cut by veins filled with a white mineral, likely calcium sulfate, that provide evidence of later episodes of fluid flow through the rocks. The panorama has been white-balanced so that the colors of the rock materials resemble how they would appear under daytime lighting conditions on Earth. It spans from southeast on the left to west on the right. The Sol 1785 location just north of the ridge is shown in a Sol 1782 traverse map. The ridge was informally named in early 2017 in memory of Vera Cooper Rubin (1928-2016), whose astronomical observations provided evidence for the existence of the universe's dark matter. An annotated figure is shown at https

  14. Effects of lake trout refuges on lake whitefish and cisco in the Apostle Islands Region of Lake Superior

    USGS Publications Warehouse

    Zuccarino-Crowe , Chiara M.; Taylor, William W.; Hansen, Michael J.; Seider, Michael J.; Krueger, Charles C.

    2016-01-01

    Lake trout refuges in the Apostle Islands region of Lake Superior are analogous to the concept of marine protected areas. These refuges, established specifically for lake trout (Salvelinus namaycush) and closed to most forms of recreational and commercial fishing, were implicated as one of several management actions leading to successful rehabilitation of Lake Superior lake trout. To investigate the potential significance of Gull Island Shoal and Devils Island Shoal refuges for populations of not only lake trout but also other fish species, relative abundances of lake trout, lake whitefish (Coregonus clupeaformis), and cisco (Coregonus artedi) were compared between areas sampled inside versus outside of refuge boundaries. During 1982–2010, lake trout relative abundance was higher and increased faster inside the refuges, where lake trout fishing was prohibited, than outside the refuges. Over the same period, lake whitefish relative abundance increased faster inside than outside the refuges. Both evaluations provided clear evidence that refuges protected these species. In contrast, trends in relative abundance of cisco, a prey item of lake trout, did not differ significantly between areas inside and outside the refuges. This result did not suggest indirect or cascading refuge effects due to changes in predator levels. Overall, this study highlights the potential of species-specific refuges to benefit other fish species beyond those that were the refuges' original target. Improved understanding of refuge effects on multiple species of Great Lakes fishes can be valuable for developing rationales for refuge establishment and predicting associated fish community-level effects.

  15. Future volcanic lake research: revealing secrets from poorly studied lakes

    NASA Astrophysics Data System (ADS)

    Rouwet, D.; Tassi, F.; Mora-Amador, R. A.

    2012-04-01

    Volcanic lake research boosted after the 1986 Lake Nyos lethal gas burst, a limnic rather than volcanic event. This led to the formation of the IAVCEI-Commission on Volcanic Lakes, which grew out into a multi-disciplinary scientific community since the 1990's. At Lake Nyos, a degassing pipe is functional since 2001, and two additional pipes were added in 2011, aimed to prevent further limnic eruption events. There are between 150 and 200 volcanic lakes on Earth. Some acidic crater lakes topping active magmatic-hydrothermal systems are monitored continuously or discontinuously. Such detailed studies have shown their usefulness in volcanic surveillance (e.g. Ruapehu, Yugama-Kusatsu-Shiran, Poás). Others are "Nyos-type" lakes, with possible gas accumulation in bottom waters and thus potentially hazardous. "Nyos-type" lakes tend to remain stably stratified in tropical and sub-tropical climates (meromictic), leading to long-term gas build-up and thus higher potential risk. In temperate climates, such lakes tend to turn over in winter (monomictic), and thus liberating its gas charge yearly. We line out research strategies for the different types of lakes. We believe a complementary, multi-disciplinary approach (geochemistry, geophysics, limnology, biology, statistics, etc.) will lead to new insights and ideas, which can be the base for future following-up and monitoring. After 25 years of pioneering studies on rather few lakes, the scientific community should be challenged to study the many poorly studied volcanic lakes, in order to better constrain the related hazard, based on probabilistic approaches.

  16. Gas exchange on Mono Lake and Crowley Lake, California

    NASA Technical Reports Server (NTRS)

    Wanninkhof, Rik; Ledwell, James R.; Broecker, Wallace S.

    1987-01-01

    Gas exchange coefficients (k) have been determined for freshwater Crowley Lake and saline Mono Lake through the use of a man-made purposefully injected gas, SF6. The concentration decreased from an initial value of 40 to 4 pmol/L for Mono Lake and from 20 to 1 pmol/L for Crowley lake over a period of 6 wks. Wind-speed (u) records from anemometers on the shore of each lake made it possible to determine the relationship between k and u. The average u and k values for the experiment were identical for the two lakes, despite the large chemical differences. It is estimated that, for the u values observed over Mono Lake from July to December 1984, the exchange of CO2 occurred 2.5 times faster than without chemical enhancement. This is a factor of 4 lower than needed to explain the high invasion rate of C-14 produced by nuclear bomb tests.

  17. Evidence for lateral mantle plume flow feeding the Central Indian Ridge

    NASA Astrophysics Data System (ADS)

    Murton, B. J.; Tindle, A. G.

    2003-04-01

    The Central Indian Ridge exhibits morphological and geochemical features indicating lateral flow of shallow plume asthenosphere from the Reunion hot-spot to the ridge axis. South of the Marie Celeste fracture zone, at 18.25°S, the Central Indian Ridge is bound by a southward closing, “V”-shaped region of shallow crust that extends for over 800 km. Over this distance, the ridge axis deepens to the south and is also affected by left-stepping offsets that bring it towards the west. The northern end of the ridge, which is closest to the island of La'Réunion, is shallowest and dominated by an inflated segment with associated sheet flows covering over 50 square kilometres. These morphological features are usually associated with ridge-hot-spot interaction. However, the nearest active hot-spot lies over 1100 km to the west beneath the island of La'Réunion. Geochemical trends for basalts erupted along the Central Indian Ridge demonstrate a gradient of northward decreasing MgO and increasing SiO2, indicating a relationship between shallower crust and increased magmatic fractional crystallisation. Superimposed on this gradient is an excess increase in incompatible element ratios, indicative of mantle enrichment to the north. The enrichment correlates with the spreading-parallel distance between the ridge axis and the edge of the "V"-shaped region of anomalously shallow crust. Locally, the enriched mantle component is found preferentially at third-order ridge offsets and adjacent to the rift walls demonstrating melting of a compositionally stratified, spinel-lherzolite mantle. These features are evidence for shallow, lateral flow of enriched hot-spot asthenosphere at a velocity of ~333 mm yr-1 and with a flux of at least 50 m3 s-1, through a mantle 'worm', towards the ridge axis where it migrates south at a rate of 54 - 67 mm per year. The trend of the geochemical enrichment points to mixing between deeper N-MORB and shallower Reunion hot-spot sources beneath the

  18. Lake

    ERIC Educational Resources Information Center

    Wien, Carol Anne

    2008-01-01

    The lake is blue black and deep. It is a glaciated finger lake, clawed out of rock when ice retracted across Nova Scotia in a northerly direction during the last ice age. The lake is narrow, a little over a mile long, and deep, 90 to 190 feet in places according to local lore, off the charts in others. The author loves to swim there, with a sense…

  19. Reconnaissance data on lakes in the Alpine Lakes Wilderness Area, Washington

    USGS Publications Warehouse

    Dethier, David P.; Heller, Paul L.; Safioles, Sally A.

    1979-01-01

    Sixty lakes in the Alpine Lakes Wilderness Area have been sampled from rubber rafts or helicopter to obtain information on their physical setting and on present water-quality conditions. The lakes are located near the crest of the Cascade Range in Chelan and King Counties, Washington. Basic data from these lakes will be useful for planners concerned with lake and wilderness management, and of interest to hikers and other recreationists who use the lakes.

  20. A V-band wafer probe using ridge-trough waveguide

    NASA Astrophysics Data System (ADS)

    Godshalk, Edward M.

    1991-12-01

    A V-band (50-75 GHz) wafer probe is presented. The probe features a type of waveguide developed to allow transition from rectangular waveguide to coplanar waveguide. The waveguide consists of a ridge extending from the upper waveguide wall into a trough in the lower waveguide wall, and is known as the ridge-trough waveguide. A mathematical model is presented that allows important properties of the ridge-trough waveguide, such as the cutoff frequency and characteristic impedance, to be calculated.

  1. Plate convergence and deformation, North Luzon Ridge, Philippines

    NASA Astrophysics Data System (ADS)

    Lewis, Stephen D.; Hayes, Dennis E.

    1989-10-01

    Marine geophysical and earthquake seismology data indicate that the North Luzon Ridge, a volcano-capped bathymetrie ridge system that extends between Luzon and Taiwan, is presently undergoing deformation in response to the relative motion between the Asian and Philippine Sea plates. Plate motion models predict convergence along the western side of the Philippine Sea plate, from Japan in the north to Indonesia in the south, and most of this plate margin is defined by active subduction zones. However, the western boundary of the Philippine Sea plate adjacent to the North Luzon Ridge shows no evidence of an active WNW-dipping subduction zone; this is in marked contrast to the presence of both the Philippine Trench/East Luzon Trough subduction zones to the south and the Ryukyu Trench subduction zone to the north. Crustal shortening, in response to ongoing plate convergence in the North Luzon Ridge region, apparently takes place through a complex pattern of strike-slip and thrust faulting, rather than by the typical subduction of oceanic lithosphere along a discreet zone. The curvilinear bathymetrie trends within the North Luzon Ridge represent the traces of active faults. The distribution of these faults, mapped by both multichannel and single-channel seismic reflection methods and earthquake seismicity patterns and focal mechanism solutions, suggest that right-lateral, oblique-slip faulting occurs along NE-trending faults, and left-lateral, oblique-slip faulting takes place on N- and NNW-trending faults. The relative plate convergence accommodated by the deformation of the North Luzon Ridge will probably be taken up in the future by the northward-propagating East Luzon Trough subduction zone.

  2. Sinuous Ridge on the Orson Welles Bajada

    NASA Image and Video Library

    2015-04-22

    Alluvial fans are piles of debris dumped by rivers when they emerge from the mountains and enter a mostly dry valley as seen by NASA Mars Reconnaissance Orbiter. A bajada (such as this example named after the famous American filmmaker) consists of a series of coalescing alluvial fans along a mountain front. On the surface of this bajada, one can see many sinuous ridges. These ridges mark the path that streams of water took as they flowed into this crater. The sinuosity of the ridges tells us something about the speed of the water flow. Fast moving flows tend to be straighter than slow-moving. Observations like this help us build a picture of how rivers behaved on ancient Mars. http://photojournal.jpl.nasa.gov/catalog/PIA19366

  3. 75 FR 20920 - Safety Zone; Lake Havasu Grand Prix, Lake Havasu, AZ

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-04-22

    ...-AA00 Safety Zone; Lake Havasu Grand Prix, Lake Havasu, AZ AGENCY: Coast Guard, DHS. ACTION: Temporary... of Lake Havasu on the Colorado River in Lake Havasu City, Arizona for the Lake Havasu Grand Prix... established in support of the Lake Havasu Grand Prix, a marine event that includes participating vessels...

  4. Reading Ombrone river delta evolution through beach ridges morphology

    NASA Astrophysics Data System (ADS)

    Mammi, Irene; Piccardi, Marco; Pranzini, Enzo; Rossi, Lorenzo

    2017-04-01

    The present study focuses on the evolution of the Ombrone River delta (Southern Tuscany, Italy) in the last five centuries, when fluvial sediment input was huge also as a consequence of the deforestation performed on the watershed. The aim of this study is to find a correlation between river input and beach ridges morphology and to explain the different distribution of wetlands and sand deposits on the two sides of the delta. Visible, NIR and TIR satellite images were processed to retrieve soil wetness associated to sand ridges and interdune silty deposits. High resolution LiDAR data were analysed using vegetation filter and GIS enhancement algorithms in order to highlight small morphological variations, especially in areas closer to the river where agriculture has almost deleted these morphologies. A topographic survey and a very high resolution 3D model obtained from a set of images acquired by an Unmanned Aerial Vehicle (UAV) were carried out in selected sites, both to calibrate satellite LiDAR 3D data, and to map low relief areas. Historical maps, aerial photography and written documents were analysed for dating ancient shorelines associated to specific beach ridges. Thus allowing the reconstruction of erosive and accretive phases of the delta. Seventy beach ridges were identified on the two wings of the delta. On the longer down-drift side (Northern wing) beach ridges are more spaced at the apex and gradually converge to the extremity, where the Bruna River runs and delimits the sub aerial depositional area of the Ombrone River. On the shorter up-drift lobe (Southern wing), beach ridges are closer, but run almost parallel each other. In this case, a rocky headland called Collelungo promontory closes and cuts the beach ridges sequence but shallow water depth allows sediment by pass. One kilometre to the south a more pronounced promontory encloses a small pocket beach (Cala di Forno) and identifies the limit of the subaerial depositionary area. Beach ridges

  5. Continental Affinities of the Alpha Ridge

    NASA Astrophysics Data System (ADS)

    Jackson, H. Ruth; Li, Qingmou; Shimeld, John; Chian, Deping

    2017-04-01

    Identifying the crustal attributes of the Alpha Ridge (AR) part of the High Arctic Large Igneous Province and tracing the spreading centre across the Amerasia Basin plays a key role in understanding the opening history of the Arctic Ocean. In this approach, we report the evidence for a continental influence on the development of the AR and reduced ocean crust in the Amerasia Basin. These points are inferred from a documented continental sedimentation source in the Amerasia Basin and calculated diagnostic compressional and shear refraction waves, and from the tracing of the distinct spreading centre using the potential field data. (1) The circum-Arctic geology of the small polar ocean provides compelling evidence of a long-lived continental landmass north of the Sverdrup Basin in the Canadian Arctic Islands and north of the Barents Sea continental margin. Based on sediment distribution patterns in the Sverdrup Basin a continental source is required from the Triassic to mid Jurassic. In addition, an extensive continental sediment source to the north of the Barents Sea is required until the Barremian. (2) Offshore data suggest a portion of continental crust in the Alpha and Mendeleev ridges including measured shear wave velocities, similarity of compressional wave velocities with large igneous province with continental fragments and magnetic patterns. Ocean bottom seismometers recorded shear waves velocities that are sensitive to the quartz content of rocks across the Chukchi Borderland and the Mendeleev Ridge that are diagnostic of both an upper and lower continental crust. On the Nautilus Spur of the Alpha Ridge expendable sonobuoys recorded clear converted shear waves also consistent with continental crust. The magnetic patterns (amplitude, frequency, and textures) on the Northwind Ridge and the Nautilus Spur also have similarities. In fact only limited portions of the deepest water portions of the Canada Basin and the Makarov Basin have typical oceanic layer 2 and

  6. Water-Balance Model to Simulate Historical Lake Levels for Lake Merced, California

    NASA Astrophysics Data System (ADS)

    Maley, M. P.; Onsoy, S.; Debroux, J.; Eagon, B.

    2009-12-01

    Lake Merced is a freshwater lake located in southwestern San Francisco, California. In the late 1980s and early 1990s, an extended, severe drought impacted the area that resulted in significant declines in Lake Merced lake levels that raised concerns about the long-term health of the lake. In response to these concerns, the Lake Merced Water Level Restoration Project was developed to evaluate an engineered solution to increase and maintain Lake Merced lake levels. The Lake Merced Lake-Level Model was developed to support the conceptual engineering design to restore lake levels. It is a spreadsheet-based water-balance model that performs monthly water-balance calculations based on the hydrological conceptual model. The model independently calculates each water-balance component based on available climate and hydrological data. The model objective was to develop a practical, rule-based approach for the water balance and to calibrate the model results to measured lake levels. The advantage of a rule-based approach is that once the rules are defined, they enhance the ability to then adapt the model for use in future-case simulations. The model was calibrated to historical lake levels over a 70-year period from 1939 to 2009. Calibrating the model over this long historical range tested the model over a variety of hydrological conditions including wet, normal and dry precipitation years, flood events, and periods of high and low lake levels. The historical lake level range was over 16 feet. The model calibration of historical to simulated lake levels had a residual mean of 0.02 feet and an absolute residual mean of 0.42 feet. More importantly, the model demonstrated the ability to simulate both long-term and short-term trends with a strong correlation of the magnitude for both annual and seasonal fluctuations in lake levels. The calibration results demonstrate an improved conceptual understanding of the key hydrological factors that control lake levels, reduce uncertainty

  7. CUTIN SYNTHASE 2 Maintains Progressively Developing Cuticular Ridges in Arabidopsis Sepals.

    PubMed

    Hong, Lilan; Brown, Joel; Segerson, Nicholas A; Rose, Jocelyn K C; Roeder, Adrienne H K

    2017-04-03

    The cuticle is a crucial barrier on the aerial surfaces of land plants. In many plants, including Arabidopsis, the sepals and petals form distinctive nanoridges in their cuticles. However, little is known about how the formation and maintenance of these nanostructures is coordinated with the growth and development of the underlying cells. Here we report the characterization of the Arabidopsis cutin synthase 2 (cus2) mutant, which causes a great reduction in cuticular ridges on the mature sepal epidermis, but only a moderate effect on petal cone cell ridges. Using scanning electron microscopy and confocal live imaging combined with quantification of cellular growth, we find that cuticular ridge formation progresses down the sepal from tip to base as the sepal grows. pCUS2::GFP-GUS reporter expression coincides with cuticular ridge formation, descending the sepal from tip to base. Ridge formation also coincides with the reduction in growth rate and termination of cell division of the underlying epidermal cells. Surprisingly, cuticular ridges at first form normally in the cus2 mutant, but are lost progressively at later stages of sepal development, indicating that CUS2 is crucial for the maintenance of cuticular ridges after they are formed. Our results reveal the dynamics of both ridge formation and maintenance as the sepal grows. Copyright © 2017 The Author. Published by Elsevier Inc. All rights reserved.

  8. Transitions in axial morphology along the Southeast Indian Ridge

    NASA Astrophysics Data System (ADS)

    Ma, Ying; Cochran, James R.

    1996-07-01

    Shipboard bathymetric and magnetic profiles across the Southeast Indian Ridge (SEIR) were analyzed in order to examine the nature of along-axis variations in axial morphology at this intermediate spreading rate ridge. Three types of axial morphology are observed along the SEIR: an axial high, a shallow (200-700 m deep) axial valley and a deep (>1000 m deep) axial valley. An axial high is found to the east of the Australian-Antarctic Discordance (AAD) (east of 128°E) and between 82°E and 104°E. A shallow rift valley is found from 104°E to 114°E and from 82°E westward past the Amerstdam/St. Paul hotspot (ASP) to about 30°S, 75°E. Deep rift valleys are found from 114°E to 128°E in the vicinity of the AAD and from the Indian Ocean Triple Junction (IOTJ) at 25°S, 70°E to about 30°S, 75°E. The transition near 30°S occurs in an area of constant zero-age depth and does not appear to result from an increase in mantle temperature. It could be the result of the rapid increase in spreading rate along that portion of the SEIR. The most likely cause of the other transitions in axial morphology is variations in mantle temperature. The transitions between the different types of axial morphology are well defined and occur over a limited distance. Transitions in axial morphology are accompanied by significant changes in ridge flank topographic roughness. The transitions from axial valleys to axial highs are also accompanied by changes in the amplitude of the seafloor magnetic anomalies. Our observations suggest that there are distinct modes rather than a continuum of axial morphology on the SEIR and that there appears to be a "threshold" mechanism for a rapid change between different states of axial morphology. The ASP has only a limited influence on the SEIR. The ridge axis is marked by an axial valley for the entire distance from the IOTJ up to and past the ASP. The ridge axis becomes shallower as the ASP is approached from the northwest but only by about 300 m over

  9. Alveolar Ridge Split Technique Using Piezosurgery with Specially Designed Tips

    PubMed Central

    Moro, Alessandro; Foresta, Enrico; Falchi, Marco; De Angelis, Paolo; D'Amato, Giuseppe; Pelo, Sandro

    2017-01-01

    The treatment of patients with atrophic ridge who need prosthetic rehabilitation is a common problem in oral and maxillofacial surgery. Among the various techniques introduced for the expansion of alveolar ridges with a horizontal bone deficit is the alveolar ridge split technique. The aim of this article is to give a description of some new tips that have been specifically designed for the treatment of atrophic ridges with transversal bone deficit. A two-step piezosurgical split technique is also described, based on specific osteotomies of the vestibular cortex and the use of a mandibular ramus graft as interpositional graft. A total of 15 patients were treated with the proposed new tips by our department. All the expanded areas were successful in providing an adequate width and height to insert implants according to the prosthetic plan and the proposed tips allowed obtaining the most from the alveolar ridge split technique and piezosurgery. These tips have made alveolar ridge split technique simple, safe, and effective for the treatment of horizontal and vertical bone defects. Furthermore the proposed piezosurgical split technique allows obtaining horizontal and vertical bone augmentation. PMID:28246596

  10. Constrained circulation at Endeavour ridge facilitates colonization by vent larvae.

    PubMed

    Thomson, Richard E; Mihály, Steven F; Rabinovich, Alexander B; McDuff, Russell E; Veirs, Scott R; Stahr, Frederick R

    2003-07-31

    Understanding how larvae from extant hydrothermal vent fields colonize neighbouring regions of the mid-ocean ridge system remains a major challenge in oceanic research. Among the factors considered important in the recruitment of deep-sea larvae are metabolic lifespan, the connectivity of the seafloor topography, and the characteristics of the currents. Here we use current velocity measurements from Endeavour ridge to examine the role of topographically constrained circulation on larval transport along-ridge. We show that the dominant tidal and wind-generated currents in the region are strongly attenuated within the rift valley that splits the ridge crest, and that hydrothermal plumes rising from vent fields in the valley drive a steady near-bottom inflow within the valley. Extrapolation of these findings suggests that the suppression of oscillatory currents within rift valleys of mid-ocean ridges shields larvae from cross-axis dispersal into the inhospitable deep ocean. This effect, augmented by plume-driven circulation within rift valleys having active hydrothermal venting, helps retain larvae near their source. Larvae are then exported preferentially down-ridge during regional flow events that intermittently over-ride the currents within the valley.

  11. Accretion mode of oceanic ridges governed by axial mechanical strength

    NASA Astrophysics Data System (ADS)

    Sibrant, A. L. R.; Mittelstaedt, E.; Davaille, A.; Pauchard, L.; Aubertin, A.; Auffray, L.; Pidoux, R.

    2018-04-01

    Oceanic spreading ridges exhibit structural changes as a function of spreading rate, mantle temperature and the balance of tectonic and magmatic accretion. The role that these or other processes have in governing the overall shape of oceanic ridges is unclear. Here, we use laboratory experiments to simulate ridge spreading in colloidal aqueous dispersions whose rheology evolves from purely viscous to elastic and brittle when placed in contact with a saline water solution. We find that ridge shape becomes increasingly linear with spreading rate until reaching a minimum tortuosity. This behaviour is predicted by the axial failure parameter ΠF, a dimensionless number describing the balance of brittle and plastic failure of axial lithosphere. Slow-spreading, fault-dominated and fast-spreading, fluid intrusion-dominated ridges on Earth and in the laboratory are separated by the same critical ΠF value, suggesting that the axial failure mode governs ridge geometry. Values of ΠF can also be calculated for different mantle temperatures and applied to other planets or the early Earth. For higher mantle temperatures during the Archaean, our results preclude the predicted formation of large tectonic plates at high spreading velocity.

  12. Alveolar Ridge Split Technique Using Piezosurgery with Specially Designed Tips.

    PubMed

    Moro, Alessandro; Gasparini, Giulio; Foresta, Enrico; Saponaro, Gianmarco; Falchi, Marco; Cardarelli, Lorenzo; De Angelis, Paolo; Forcione, Mario; Garagiola, Umberto; D'Amato, Giuseppe; Pelo, Sandro

    2017-01-01

    The treatment of patients with atrophic ridge who need prosthetic rehabilitation is a common problem in oral and maxillofacial surgery. Among the various techniques introduced for the expansion of alveolar ridges with a horizontal bone deficit is the alveolar ridge split technique. The aim of this article is to give a description of some new tips that have been specifically designed for the treatment of atrophic ridges with transversal bone deficit. A two-step piezosurgical split technique is also described, based on specific osteotomies of the vestibular cortex and the use of a mandibular ramus graft as interpositional graft. A total of 15 patients were treated with the proposed new tips by our department. All the expanded areas were successful in providing an adequate width and height to insert implants according to the prosthetic plan and the proposed tips allowed obtaining the most from the alveolar ridge split technique and piezosurgery. These tips have made alveolar ridge split technique simple, safe, and effective for the treatment of horizontal and vertical bone defects. Furthermore the proposed piezosurgical split technique allows obtaining horizontal and vertical bone augmentation.

  13. Tectonic evolution of Gorda Ridge inferred from sidescan sonar images

    USGS Publications Warehouse

    Masson, D.G.; Cacchione, D.A.; Drake, D.E.

    1988-01-01

    Gorda Ridge is the southern segment of the Juan de Fuca Ridge complex, in the north-east Pacific. Along-strike spreading-rate variation on Gorda Ridge and deformation of Gorda Plate are evidence for compression between the Pacific and Gorda Plates. GLORIA sidescan sonographs allow the spreading fabric associated with Gorda Ridge to be mapped in detail. Between 5 and 2 Ma, a pair of propagating rifts re-orientated the northern segment of Gorda Ridge by about 10?? clockwise, accommodating a clockwise shift in Pacific-Juan de Fuca plate motion that occurred around 5 Ma. Deformation of Gorda Plate, associated with southward decreasing spreading rates along southern Gorda Ridge, is accommodated by a combination of clockwise rotation of Gorda Plate crust, coupled with left-lateral motion on the original normal faults of the ocean crust. Segments of Gorda Plate which have rotated by different amounts are separated by narrow deformation zones across which sharp changes in ocean fabric trend are seen. Although minor lateral movement may occur on these NW to WNW structures, no major right-lateral movement, as predicted by previous models, is observed. ?? 1988 Kluwer Academic Publishers.

  14. Zinc, copper, and lead in mid-ocean ridge basalts and the source rock control on Zn/Pb in ocean-ridge hydrothermal deposits

    USGS Publications Warehouse

    Doe, B.R.

    1994-01-01

    The contents of Zn, Cu, and Pb in mid-ocean ridge basalts (MORB) and the MORB source-rock control on Zn/Pb in ocean-ridge hydrothermal deposits are examined. The values of Zn, Cu, and Pb for submarine mid-ocean ridge basalts (MORB) are, respectively (in ppm): average MORB-75, 75, and 0.7; West Valley, Juan de Fuca Ridge (JFR)-87, 64, and 0.5; southern JFR-120 and 0.5; and 21??N, East Pacific Rise (EPR)-73, 78, and 0.5. Values of Zn/Pb range from about 100-240 and Cu/ Pb from 100-156. In this study, Zn is found to correlate positively with TiO2 + FeO (mean square of weighted deviates, MSWD, of 1.6 for JFR basalt), and inversely with Mg number (MSWD of 3.5). Therefore, contrary to statements in the literature that Zn should be compatible in MORB, Zn is a mildly incompatible element and must be enriched in the glass phase relative to olivine as Zn does not fit into the other major phenocryst phase, plagioclase. In the source of MORB, Zn likely is most enriched in oxides: spinel, magnetite, and titanomagnetite. Copper generally does not correlate well with other elements in most MORB data examined. When differentiation is dominated by olivine, Cu has a tendency to behave incompatibly (e.g., at Mg numbers > 70), but, overall, Cu shows some tendency towards being a compatible element, particularly along the Mid-Atlantic Ridge, a behavior presumably due to separation of sulfides in which Cu (but not Zn) is markedly enriched. Copper thus may be in dispersed sulfides in the source of MORB. Ocean ridges provide important data on source-rock controls for sulfide deposits because, in sediment-starved ridges, much is known about the possible source rocks and mineralization is presently occurring. In contrast to Zn/Pb ~5 in continental hot Cl-rich brines, Zn/Pb in the hottest sediment-starved ridge black smoker hydrothermal fluids at 21 ??N, EPR is about 110, similar to local MORB (145), but Cu/Pb is closer to 30, possibly due to subsurface deposition of Cu. At the JFR, the best

  15. White Lake AOC

    EPA Pesticide Factsheets

    White Lake is in Muskegon County along the eastern shore of Lake Michigan. It was named an Area of Concern on the Great Lakes under the Great Lakes Water Quality Agreement of 1987 and delisted in 2014.

  16. Pronounced Shear Velocity Asymmetry in the Mantle Across the Juan de Fuca Ridge and Curious Lack of Features at the Gorda Ridge

    NASA Astrophysics Data System (ADS)

    Bell, S. W.; Ruan, Y.; Forsyth, D. W.

    2015-12-01

    With new Rayleigh-wave tomography results, we have detected a clear and strong asymmetry in the shear velocity structure of the Juan de Fuca ridge. Concentrated in a relatively thin layer with a depth range of ~30-60km, there lies a region of very low shear velocity, with velocities ranging from ~3.8km/s to 4.0km/s. Such low velocities provide strong evidence for the presence of partial melt. This low-velocity region is highly asymmetric, extending much further west than east of the ridge. Especially at shallow depths of ~35 km, this low-velocity region is concentrated just west of the southern portion of the ridge. Peaking near the Axial Seamount, the youngest of the Cobb-Eickelberg Seamounts, it extends south to the region around the small Vance Seamounts just north of the junction with the Blanco Fracture Zone. The Juan de Fuca plate is relatively stationary in the hotspot reference frame, and the Juan de Fuca ridge migrates westward in the hotspot reference frame. Seamounts are overwhelmingly concentrated on the western flank of the ridge, and an asymmetric upwelling driven by migration in the hotspot reference frame has been proposed to explain the seamount asymmetry (i.e. Davis and Karsten, 1986). Our velocity asymmetry, which matches the seamount asymmetry, provides evidence for this asymmetric upwelling and its connection to migration in the absolute hotspot reference frame. In the shear velocity results, the Gorda ridge displays a remarkable lack of features, with no clearly identifiable expression in the subsurface velocity. There is evidence of a broad low-velocity feature beneath Gorda beginning at a depth of ~150 km, but no clear shallow features can be tied to the ridge. At the depths we can resolve (~25-250km), the anisotropy beneath and within the Juan de Fuca plate is small, indicating a deep source of the shear wave splitting results (Bodmer et al., in press), which indicate a fast axis aligned with the Juan de Fuca plate's absolute motion. Around

  17. Solar cell with doped groove regions separated by ridges

    DOEpatents

    Molesa, Steven Edward; Pass, Thomas; Kraft, Steve

    2017-01-31

    Solar cells with doped groove regions separated by ridges and methods of fabricating solar cells are described. In an example, a solar cell includes a substrate having a surface with a plurality of grooves and ridges. A first doped region of a first conductivity type is disposed in a first of the grooves. A second doped region of a second conductivity type, opposite the first conductivity type, is disposed in a second of the grooves. The first and second grooves are separated by one of the ridges.

  18. In-lake Modeling Recommendation Report for Lake Champlain TMDL

    EPA Pesticide Factsheets

    This report describes the recommended modeling approach for the in-lake modeling component of the Lake Champlain TMDL project. The report was prepared by Tetra Tech, with input from the Lake Champlain modeling workgroup. (TetraTech, 2012b)

  19. 2005 Tri-Service Infrastructure Systems Conference and Exhibition. Volume 5, Track 5

    DTIC Science & Technology

    2005-08-04

    Patrick O’Brien and David Biedenharn Watershed Approach to Stream Stability and Benefits Related to the Reduction of Nutrients, by John B. Smith A Lake ...J.B. Smith and Randall A. Wise Bluff Stabilization along Lake Michigan, using Active and Passive Dewatering Techniques, by Rennie Kaunda, Eileen...Sacred Falls, Oahsacred Falls, Oahu Section 227 Demonstration Project Track 4 Fern Ridge LakFern Ridge Lake Hydrologic Aspects of Operation during Failure

  20. Water quality of Lake Austin and Town Lake, Austin, Texas

    USGS Publications Warehouse

    Andrews, Freeman L.; Wells, Frank C.; Shelby, Wanda J.; McPherson, Emma

    1988-01-01

    Water-quality data collected from Lake Austin and Town Lake, following runoff, generally were not adequate to fully determine the effects of runoff on the lakes. Data collection should not to be limited to fixed-station sampling following runoff, and both lakes need to be sampled simultaneously as soon as possible following significant precipitation.

  1. Bathymetry of Bonnie Doone Lake, Kornbow Lake, Mintz Pond, and Glenville Lake, Cumberland County, North Carolina, 1996-98

    USGS Publications Warehouse

    Giorgino, M.J.; Strain, R.E.

    1999-01-01

    Bathymetric surveys were conducted at four water-supply impoundments of Little Cross Creek in Cumberland County, North Carolina. The surveys were conducted in April 1996 at Mintz Pond and Glenville Lake, and in January 1998 at Bonnie Doone Lake and Kornbow Lake. The resulting bathymetric maps are the first to cover the entire range in depth for these reservoirs and provide a framework for future evaluations of bathymetry and storage capacity. Bathymetric maps were constructed from depth and position data collected at each reservoir. A boat-mounted, research-grade fathometer was used to record water depths with a vertical accuracy of 0.1 foot. At Mintz Pond and Glenville Lake, position was measured by using a wide-band laser tracking system interfaced with a total station survey instrument. This positioning method required multiple land-based control points to be established and was hampered by line-of-sight restrictions between the control points and the boat. At Bonnie Doone Lake and Kornbow Lake, a global positioning system was used to collect differentially corrected location data. This positioning method enabled more rapid data collection, eliminated the need for land-based control points, and provided improved data coverage. Spillway elevations range from 172.8 feet above mean sea level at Bonnie Doone Lake to 113.1 feet at Glenville Lake. Surface area and storage volume were computed for each reservoir and were related to water-surface elevations at 1-foot intervals. The combined surface acreage of the four Little Cross Creek reservoirs at their full-pool elevations is 120.97 acres, consisting of 21.20 acres at Bonnie Doone Lake, 47.09 acres at Kornbow Lake, 15.56 acres at Mintz Pond, and 37.12 acres at Glenville Lake. The four reservoirs have a combined usable storage capacity of 674.91 acre-feet, which is the sum of 127.93 acre-feet in Bonnie Doone Lake, 320.62 acre-feet in Kornbow Lake, 53.25 acre-feet in Mintz Pond, and 173.11 acre-feet in Glenville Lake.

  2. Magma Supply at the Arctic Gakkel Ridge: Constraints from Peridotites and Basalts

    NASA Astrophysics Data System (ADS)

    Sun, C.; Dick, H. J.; Hellebrand, E.; Snow, J. E.

    2015-12-01

    Crustal thickness in global ridge systems is widely believed to be nearly uniform (~7 km) at slow- and fast-spreading mid-ocean ridges, but appears significantly thinner (< ~4 km) at ultraslow-spreading ridges. At the slowest-spreading Arctic Gakkel Ridge, the crust becomes extremely thin (1.4 - 2.9 km; [1]). The thin crust at the Gakkel and other ultraslow-spreading ridges, has been attributed to lithosphere thickening, ancient mantle depletion, lower mantle temperature, ridge obliquity, and melt retention/focusing. To better understand the magma supply at ultraslow-spreading ridges, we examined melting dynamics by linking peridotites and basalts dredged along the Gakkel Ridge. We analyzed rare earth elements in clinopyroxene from 84 residual peridotites, and estimated melting parameters for individual samples through nonlinear least squares analyses. The degrees of melting show a large variation but mainly center at around 7% assuming a somewhat arbitrary but widely used depleted MORB mantle starting composition. Thermobarometry on published primitive basaltic glasses from [2] indicates that the mantle potential temperature at the Gakkel Ridge is ~50°C cooler than that at the East Pacific Rise. The ridge-scale low-degree melting and lower mantle potential temperature place the final depth of melting at ~30 km and a melt thickness of 1.0 or 2.9 km for a triangular or trapezoidal melting regime, respectively. The final melting depth is consistent with excess conductive cooling and lithosphere thickening suggested by geodynamic models, while the estimated melt thickness is comparable to the seismic crust (1.4 - 2.9 km; [1]). The general agreement among geochemical analyses, seismic measurements, and geodynamic models supports that lower mantle potential temperature and thick lithosphere determine the ridge-scale low-degree melting and thin crust at the Gakkel Ridge, while melt retention/focusing and excess ancient mantle depletion are perhaps locally important at

  3. Beach ridge sedimentology: field observation and palaeoenvironmental interpretation for Anegada Island, British Virgin Islands.

    NASA Astrophysics Data System (ADS)

    Cescon, Anna Lisa; Cooper, J. Andrew G.; Jackson, Derek W. T.

    2014-05-01

    Beach ridge landforms have been observed in different environments and in settings that range from polar to tropical. Their stratigraphy and sedimentology has received a limited amount of discussion in the literature (Tamura, 2012). In coastal geomorphology a beach ridge can be seen as a transitional deposit between onshore and offshore environments. They are regarded as representing high level wave action along a coastline. In the Caribbean the origin of beach ridges has been variously attributed to one of three extreme wave events: extreme swell, extreme storm or tsunami waves. Beach ridges are arranged in beach ridge plains where there is succession of the landforms and can be several kilometres long. Beach ridge accumulation is not continuous and the coast shows alternating accretion and erosion periods. The use of beach ridges as palaeostorm archives is therefore not straightforward. The temporal continuity of beach ridge formation is being assessed on the beach ridge plains of Anegada, British Virgin Islands (Lesser Antilles). This carbonate platform surrounded by a fringing reef contains two beach ridge plains. There are more than 30 ridges in the Atlantic facing- coast and around 10 in the south, Caribbean- facing coast. The sediments of the modern beaches are dominated by the sand fraction and are 100% biogenic origin due to the isolation of Anegada from terrestrial sediment sources. The beach ridge sections have been studied in different area of Anegada beach ridge plains and present low angle seaward-dipping bedding. The sand fraction is dominant in the stratigraphy with a few intact shells. At only one site were coral pebbles deposited in association with the sand fraction. Aeolian deposits represent the upper part of the beach ridges and reflect the stabilization of the beach ridges with ongoing accretion. The sedimentology of the contemporary beach and dunes will be discussed in terms of their implications for understanding beach ridge genesis and its

  4. Microbial Mat Communities along an Oxygen Gradient in a Perennially Ice-Covered Antarctic Lake

    PubMed Central

    Hawes, Ian; Mackey, Tyler J.; Krusor, Megan; Doran, Peter T.; Sumner, Dawn Y.; Eisen, Jonathan A.; Hillman, Colin; Goroncy, Alexander K.

    2015-01-01

    Lake Fryxell is a perennially ice-covered lake in the McMurdo Dry Valleys, Antarctica, with a sharp oxycline in a water column that is density stabilized by a gradient in salt concentration. Dissolved oxygen falls from 20 mg liter−1 to undetectable over one vertical meter from 8.9- to 9.9-m depth. We provide the first description of the benthic mat community that falls within this oxygen gradient on the sloping floor of the lake, using a combination of micro- and macroscopic morphological descriptions, pigment analysis, and 16S rRNA gene bacterial community analysis. Our work focused on three macroscopic mat morphologies that were associated with different parts of the oxygen gradient: (i) “cuspate pinnacles” in the upper hyperoxic zone, which displayed complex topography and were dominated by phycoerythrin-rich cyanobacteria attributable to the genus Leptolyngbya and a diverse but sparse assemblage of pennate diatoms; (ii) a less topographically complex “ridge-pit” mat located immediately above the oxic-anoxic transition containing Leptolyngbya and an increasing abundance of diatoms; and (iii) flat prostrate mats in the upper anoxic zone, dominated by a green cyanobacterium phylogenetically identified as Phormidium pseudopriestleyi and a single diatom, Diadesmis contenta. Zonation of bacteria was by lake depth and by depth into individual mats. Deeper mats had higher abundances of bacteriochlorophylls and anoxygenic phototrophs, including Chlorobi and Chloroflexi. This suggests that microbial communities form assemblages specific to niche-like locations. Mat morphologies, underpinned by cyanobacterial and diatom composition, are the result of local habitat conditions likely defined by irradiance and oxygen and sulfide concentrations. PMID:26567300

  5. Microbial Mat Communities along an Oxygen Gradient in a Perennially Ice-Covered Antarctic Lake.

    PubMed

    Jungblut, Anne D; Hawes, Ian; Mackey, Tyler J; Krusor, Megan; Doran, Peter T; Sumner, Dawn Y; Eisen, Jonathan A; Hillman, Colin; Goroncy, Alexander K

    2016-01-15

    Lake Fryxell is a perennially ice-covered lake in the McMurdo Dry Valleys, Antarctica, with a sharp oxycline in a water column that is density stabilized by a gradient in salt concentration. Dissolved oxygen falls from 20 mg liter(-1) to undetectable over one vertical meter from 8.9- to 9.9-m depth. We provide the first description of the benthic mat community that falls within this oxygen gradient on the sloping floor of the lake, using a combination of micro- and macroscopic morphological descriptions, pigment analysis, and 16S rRNA gene bacterial community analysis. Our work focused on three macroscopic mat morphologies that were associated with different parts of the oxygen gradient: (i) "cuspate pinnacles" in the upper hyperoxic zone, which displayed complex topography and were dominated by phycoerythrin-rich cyanobacteria attributable to the genus Leptolyngbya and a diverse but sparse assemblage of pennate diatoms; (ii) a less topographically complex "ridge-pit" mat located immediately above the oxic-anoxic transition containing Leptolyngbya and an increasing abundance of diatoms; and (iii) flat prostrate mats in the upper anoxic zone, dominated by a green cyanobacterium phylogenetically identified as Phormidium pseudopriestleyi and a single diatom, Diadesmis contenta. Zonation of bacteria was by lake depth and by depth into individual mats. Deeper mats had higher abundances of bacteriochlorophylls and anoxygenic phototrophs, including Chlorobi and Chloroflexi. This suggests that microbial communities form assemblages specific to niche-like locations. Mat morphologies, underpinned by cyanobacterial and diatom composition, are the result of local habitat conditions likely defined by irradiance and oxygen and sulfide concentrations. Copyright © 2016, American Society for Microbiology. All Rights Reserved.

  6. Oak Ridge TNS Program: system description manual

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Reid, R.L.; Becraft, W.R.; Brown, T.G.

    1979-05-01

    This document provides a systems description of the Reference Design for The Next Step (TNS) evolved at Oak Ridge National Laboratory (ORNL) during FY 1978. The description is presented on the basis of 24 individual device and facility systems. Additional information on these systems, the Reference Design, and the FY 1978 Oak Ridge TNS activities can be found in the associated technical memoranda, ORNL/TM-6720 and ORNL/TM-6722--ORNL/TM-6733.

  7. Lake trout in the Great Lakes: Basin-wide stock collapse and binational restoration

    USGS Publications Warehouse

    Hansen, Michael J.; Taylor, William W.; Ferreri, C. Paola

    1999-01-01

    The lake trout (Salvelinus namaycush) was important to the human settlement of each of the Great Lakes, and underwent catastrophic collapses in each lake in the nineteenth and twentieth centuries. The timing of lake trout stock collapses were different in each lake, as were the causes of the collapses, and have been the subject of much scientific inquiry and debate. The purpose of this chapter is to summarize and review pertinent information relating historical changes in Great Lakes lake trout stocks, binational efforts to restore those stocks, and progress toward stock restoration. This presentation attempts to generalize patterns across the Great Lakes, rather than to focus within each lake. Lake specific analyses have been used to understand lake specific causes and effects, but there is continuing debate about some of these causes and effects. A basinwide review may suggest mechanisms for observed changes that are not evident by lake specific analysis.

  8. GloboLakes: A global observatory of lake responses to environmental change.

    NASA Astrophysics Data System (ADS)

    Groom, Steve; Tyler, Andrew; Hunter, Peter; Spyrakos, Evangelos; Martinez-Vicente, Victor; Merchant, Chris; Cutler, Mark; Rowan, John; Dawson, Terry; Maberly, Stephen; Cavalho, Laurence; Elliot, Alex; Thackery, Stephen; Miller, Claire; Scott, Marian

    2014-05-01

    The world's freshwater ecosystems are vital components of the global biosphere, yet are vulnerable to climate and other human-induced change. There is increasing recognition that lakes play an important role in global biogeochemical cycling and provide key ecosystem services. However, our understanding of how lakes respond to environmental change at a global scale, and how this impacts on their status and function, is hampered by limited information on their chemical, physical and ecological condition. There are estimated to be over 300 million lakes globally, of which over 17,000 are greater than 10 km2 in surface area. These numbers have limited the systematic study of lake ecosystems. GloboLakes is a five-year UK research programme investigating the state of lakes and their response to climatic and other environmental drivers of change. It will establish a satellite-based observatory with archive and near-real time data processing to produce a time series of observed biogeochemical parameters and lake temperature for over 1000 lakes globally. This will be supported by linked ancillary data on climate and catchment land-use. The ability to monitor a large number of lakes consistently at high frequency and globally will facilitate a paradigm shift in our understanding of how lakes respond to environmental change at different spatial and temporal scales. A key requirement is to validate satellite retrieval algorithms and test the time-series of resulting lake properties such as chlorophyll-a by comparison with in situ data. To support the former extensive bio-optical and constituent data were taken in year 1 of the project in a number of UK lakes with a variety of trophic states. Furthermore, for wider validation activities GloboLakes has established the LIMNADES initiative to create a centralised database of ground bio-optical measurements of worldwide lakes through voluntary cooperation across the international scientific community. This presentation will

  9. Ridge-trench collision in Archean and Post-Archean crustal growth: Evidence from southern Chile

    NASA Technical Reports Server (NTRS)

    Nelson, E. P.; Forsythe, R. D.

    1988-01-01

    The growth of continental crust at convergent plate margins involves both continuous and episodic processes. Ridge-trench collision is one episodic process that can cause significant magmatic and tectonic effects on convergent plate margins. Because the sites of ridge collision (ridge-trench triple junctions) generally migrate along convergent plate boundaries, the effects of ridge collision will be highly diachronous in Andean-type orogenic belts and may not be adequately recognized in the geologic record. The Chile margin triple junction (CMTJ, 46 deg S), where the actively spreading Chile rise is colliding with the sediment-filled Peru-Chile trench, is geometrically and kinematically the simplest modern example of ridge collision. The south Chile margin illustrates the importance of the ridge-collision tectonic setting in crustal evolution at convergent margins. Similarities between ridge-collision features in southern Chile and features of Archean greenstone belts raise the question of the importance of ridge collision in Archean crustal growth. Archean plate tectonic processes were probably different than today; these differences may have affected the nature and importance of ridge collision during Archean crustal growth. In conclusion, it is suggested that smaller plates, greater ridge length, and/or faster spreading all point to the likelihood that ridge collision played a greater role in crustal growth and development of the greenstone-granite terranes during the Archean. However, the effects of modern ridge collision, and the processes involved, are not well enough known to develop specific models for the Archean ridge collison.

  10. Ridge-branch-based blood vessel detection algorithm for multimodal retinal images

    NASA Astrophysics Data System (ADS)

    Li, Y.; Hutchings, N.; Knighton, R. W.; Gregori, G.; Lujan, B. J.; Flanagan, J. G.

    2009-02-01

    Automatic detection of retinal blood vessels is important to medical diagnoses and imaging. With the development of imaging technologies, various modals of retinal images are available. Few of currently published algorithms are applied to multimodal retinal images. Besides, the performance of algorithms with pathologies is expected to be improved. The purpose of this paper is to propose an automatic Ridge-Branch-Based (RBB) detection algorithm of blood vessel centerlines and blood vessels for multimodal retinal images (color fundus photographs, fluorescein angiograms, fundus autofluorescence images, SLO fundus images and OCT fundus images, for example). Ridges, which can be considered as centerlines of vessel-like patterns, are first extracted. The method uses the connective branching information of image ridges: if ridge pixels are connected, they are more likely to be in the same class, vessel ridge pixels or non-vessel ridge pixels. Thanks to the good distinguishing ability of the designed "Segment-Based Ridge Features", the classifier and its parameters can be easily adapted to multimodal retinal images without ground truth training. We present thorough experimental results on SLO images, color fundus photograph database and other multimodal retinal images, as well as comparison between other published algorithms. Results showed that the RBB algorithm achieved a good performance.

  11. Ultra-fast pulse propagation in nonlinear graphene/silicon ridge waveguide

    NASA Astrophysics Data System (ADS)

    Liu, Ken; Zhang, Jian Fa; Xu, Wei; Zhu, Zhi Hong; Guo, Chu Cai; Li, Xiu Jian; Qin, Shi Qiao

    2015-11-01

    We report the femtosecond laser propagation in a hybrid graphene/silicon ridge waveguide with demonstration of the ultra-large Kerr coefficient of graphene. We also fabricated a slot-like graphene/silicon ridge waveguide which can enhance its effective Kerr coefficient 1.5 times compared with the graphene/silicon ridge waveguide. Both transverse-electric-like (TE-like) mode and transverse-magnetic-like (TM-like) mode are experimentally measured and numerically analyzed. The results show nonlinearity dependence on mode polarization not in graphene/silicon ridge waveguide but in slot-like graphene/silicon ridge waveguide. Great spectral broadening was observed due to self-phase modulation (SPM) after propagation in the hybrid waveguide with length of 2 mm. Power dependence property of the slot-like hybrid waveguide is also measured and numerically analyzed. The results also confirm the effective Kerr coefficient estimation of the hybrid structures. Spectral blue shift of the output pulse was observed in the slot-like graphene/silicon ridge waveguide. One possible explanation is that the blue shift was caused by the ultra-fast free carrier effect with the optical absorption of the doped graphene. This interesting effect can be used for soliton compression in femtosecond region. We also discussed the broadband anomalous dispersion of the Kerr coefficient of graphene.

  12. Mechanics of gravitational spreading of steep-sided ridges («sackung»)

    USGS Publications Warehouse

    Savage, W.Z.; Varnes, D.J.

    1987-01-01

    Large-scale gravitational spreading of steep-sided ridges characterized by linear fissures, trenches, and uphill-facing scarps high on the sides and tops of ridges are known worldwide. Such spreading, termed sackung, is commonly attributed to pervasive plastic deformation of a rock mass, and is here analyzed as such. Beginning with a previously developed exact elastic solution for gravity-induced stresses in a symmetric ridge, stresses calculated from the exact solution are used in the Coulomb failure criterion to determine the extent of ridge failure under self-weight. Finally, when the regions of failure are established, a plastic flow solution is applied to predict the location of and sense of movement on upward-facing scarps near ridge crests and other features common in sackung. ?? 1987 International Assocaition of Engineering Geology.

  13. Melton Valley Storage Tanks Capacity Increase Project, Oak Ridge National Laboratory, Oak Ridge, Tennessee

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    NONE

    1995-04-01

    The US Department of Energy (DOE) proposes to construct and maintain additional storage capacity at Oak Ridge National Laboratory (ORNL), Oak Ridge, Tennessee, for liquid low-level radioactive waste (LLLW). New capacity would be provided by a facility partitioned into six individual tank vaults containing one 100,000 gallon LLLW storage tank each. The storage tanks would be located within the existing Melton Valley Storage Tank (MVST) facility. This action would require the extension of a potable water line approximately one mile from the High Flux Isotope Reactor (HFIR) area to the proposed site to provide the necessary potable water for themore » facility including fire protection. Alternatives considered include no-action, cease generation, storage at other ORR storage facilities, source treatment, pretreatment, and storage at other DOE facilities.« less

  14. The Effects of Ridge Axis Width on Mantle Melting at Mid-Ocean Ridges

    NASA Astrophysics Data System (ADS)

    Montesi, L.; Magni, V.; Gaina, C.

    2017-12-01

    Mantle upwelling in response to plate divergence produces melt at mid-ocean ridges. Melt starts when the solidus is crossed and stops when conductive cooling overcomes heat advection associated with the upwelling. Most mid-ocean ridge models assume that divergence takes place only in a narrow zone that defines the ridge axis, resulting in a single upwelling. However, more complex patterns of divergence are occasionally observed. The rift axis can be 20 km wide at ultraslow spreading center. Overlapping spreading center contain two parallel axes. Rifting in backarc basins is sometimes organized as a series of parallel spreading centers. Distributing plate divergence over several rifts reduces the intensity of upwelling and limits melting. Can this have a significant effect on the expected crustal thickness and on the mode of melt delivery at the seafloor? We address this question by modeling mantle flow and melting underneath two spreading centers separated by a rigid block. We adopt a non-linear rheology that includes dislocation creep, diffusion creep and yielding and include hydrothermal cooling by enhancing thermal conductivity where yielding takes place. The crustal thickness decreases if the rifts are separated by 30 km or more but only if the half spreading rate is between 1 and 2 cm/yr. At melting depth, a single upwelling remains the norm until the separation of the rifts exceeds a critical value ranging from 15 km in the fastest ridges to more than 50 km at ultraslow spreading centers. The stability of the central upwelling is due to hydrothermal cooling, which prevents hot mantle from reaching the surface at each spreading center. When hydrothermal cooling is suppressed, or the spreading centers are sufficiently separated, the rigid block becomes extremely cold and separates two distinct, highly asymmetric upwellings that may focus melt beyond the spreading center. In that case, melt delivery might drive further and further the divergence centers, whereas

  15. Noachian Impact Ejecta on Murray Ridge and Pre-impact Rocks on Wdowiak Ridge, Endeavour Crater, Mars: Opportunity Observations

    NASA Technical Reports Server (NTRS)

    Mittlefehldt, D. W.; Gellert, R.; Ming, D. W.; Morris, R. V.; Schroeder, C.; Yen, A. S.; Farrand, W. H.; Arvidson, R. E.; Franklin, B. J.; Grant, J. A.; hide

    2015-01-01

    Mars Exploration Rover Opportunity has been exploring Meridiani Planum since January 2004, and has completed 4227% of its primary mission. Opportunity has been investigating the geology of the rim of 22 km diameter Endeavour crater, first on the Cape York segment and now on Cape Tribulation. The outcrops are divided York; (ii) the Shoemaker fm, impact breccias representing ejecta from the crater; into three formations: (i) the lower Matijevic fm, a pre-impact lithology on Cape and (iii) the upper Grasberg fm, a post-impact deposit that drapes the lower portions of the eroded rim segments. On the Cape Tribulation segment Opportunity has been studying the rocks on Murray Ridge, with a brief sojourn to Wdowiak Ridge west of the rim segment. team member Thomas Wdowiak, who died in 2013.) One region of Murray Ridge has distinctive CRISM spectral characteristics indicating the presence of a small concentration of aluminous smectite based on a 2.2 micron Al-OH combination band (hereafter, the Al-OH region).

  16. Pelagic erosion and sedimentation north of Carnegie Ridge, eastern equatorial Pacific

    NASA Astrophysics Data System (ADS)

    Brooks, C. K.; Lyle, M. W.; Marcantonio, F.; Lewis, D. M.; Paul, C.

    2011-12-01

    The Carnegie Ridge is one of three bathymetric highs bounding the Panama Basin and is known to exhibit erosion and redeposition of pelagic sediments. The extent of erosion and redeposition was studied during the R/V Melville cruise MV1014 in November 2010 to compare with geochemical estimates of sediment focusing. The MV1014 cruise acquired geochemical, geological and geophysical data using multichannel 2-D seismic and 3.5 kHz sub-bottom profiler, swathmap bathymetry, coring, and water casts. The seismic reflection, digital sub-bottom profiler and swathmap bathymetry data were used to investigate biogenic sedimentary deposition in the Panama Basin and erosion from Carnegie Ridge. We compare the new geophysical results with drilling on ODP Leg 202, the NEMO-03 site survey cruise for Leg 202, an early survey from 1969 and other data compiled by Ecuadorian surveys. Areas of non-deposition and/or erosion include the bathymetric highs along the ridge, seamounts, and an area of interest, a valley located on the northwestern flank of the ridge. The valley encompasses 183 km2 and exhibits large scale erosion, cutting down through sediments deposited over the 10-million year life of this segment of the Carnegie Ridge. All other valleys located within the Carnegie Ridge study area demonstrate ample deposition with sedimentary packages ranging from 200-800m with an average value trending around 400m. Higher sediment deposition is found in basins to the north of the erosional valley but similar sedimentation is also found even further north, beyond intervening high topography. The thickest sediment deposit near the Carnegie Ridge is actually found on the southern flank of the ridge, more than 100 km to the south of the survey area. Digital chirp sub-bottom profiler data combined with high-resolution seismic illustrate changes in sedimentation and erosion on the Carnegie Ridge, highlighting the dynamic sedimentary environment.

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

    NASA Astrophysics Data System (ADS)

    Schultz, R. A.

    1989-10-01

    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.

  18. New Progress on Radiocarbon Geochronology in Southern Lake Tanganyika (East Africa)

    NASA Astrophysics Data System (ADS)

    McGlue, M. M.; Soreghan, M. J.

    2017-12-01

    Our limnogeological research in Lake Tanganyika focuses on elucidating the patterns of sediment accumulation on deepwater horsts, outer platforms, and littoral environments in the lake's southern basin ( 6-8°S latitude). Here, we present new radiocarbon (14C) dates from high-quality surface sediment cores, in order to make comparisons with previously published age models, to address the presence and spatiotemporal variability of a reservoir effect, and to constrain sedimentation rates and facies at sites that may be important targets for future scientific drilling. Plant macrofossils are rare in deepwater sediment cores, so charcoal and bulk organic matter have been the primary materials used for dating. On the Kavala Island Ridge (KIR) horst, initial core descriptions revealed variations in laminae presence, thickness, and chemistry. Sediment cores from the KIR at 172m water depth consist of thickly laminated diatom oozes. Charcoal from the bases of these cores returned median ages of 2.1-2.2 cal ka, suggesting linear accumulation rates on the order of 0.51 mm/yr. By contrast, a core from 420 m water depth on the KIR exhibited very thin laminations and diatom layers were much less prominent. Charcoal at the base of this core produced a median age of 8.1 cal ka, suggesting a linear accumulation rate of 0.11 mm/yr. These initial results suggest that sedimentation rates may vary considerably over sublacustrine horst blocks. We will test this initial discovery with additional sedimentation rate information from the Kalya and Nitiri horsts. In addition, we report new 14C dates made on both dead and live-collected shells of the endemic gastropod Neothauma tanganyicense. These shells form vast accumulations along shallow-water platforms of the lake and form an important substrate for a number of other endemic species. The discovery of living snails in southern Lake Tanganyika may allow for the development of a species-specific reservoir correction. A limited N

  19. Evidence for chemically heterogeneous Arctic mantle beneath the Gakkel Ridge

    NASA Astrophysics Data System (ADS)

    D'Errico, Megan E.; Warren, Jessica M.; Godard, Marguerite

    2016-02-01

    Ultraslow spreading at mid-ocean ridges limits melting due to on-axis conductive cooling, leading to the prediction that peridotites from these ridges are relatively fertile. To test this, we examined abyssal peridotites from the Gakkel Ridge, the slowest spreading ridge in the global ocean ridge system. Major and trace element concentrations in pyroxene and olivine minerals are reported for 14 dredged abyssal peridotite samples from the Sparsely Magmatic (SMZ) and Eastern Volcanic (EVZ) Zones. We observe large compositional variations among peridotites from the same dredge and among dredges in close proximity to each other. Modeling of lherzolite trace element compositions indicates varying degrees of non-modal fractional mantle melting, whereas most harzburgite samples require open-system melting involving interaction with a percolating melt. All peridotite chemistry suggests significant melting that would generate a thick crust, which is inconsistent with geophysical observations at Gakkel Ridge. The refractory harzburgites and thin overlying oceanic crust are best explained by low present-day melting of a previously melted heterogeneous mantle. Observed peridotite compositional variations and evidence for melt infiltration demonstrates that fertile mantle components are present and co-existing with infertile mantle components. Melt generated in the Gakkel mantle becomes trapped on short length-scales, which produces selective enrichments in very incompatible rare earth elements. Melt migration and extraction may be significantly controlled by the thick lithosphere induced by cooling at such slow spreading rates. We propose the heterogeneous mantle that exists beneath Gakkel Ridge is the consequence of ancient melting, combined with subsequent melt percolation and entrapment.

  20. Buldir Depression - A Late Tertiary graben on the Aleutian Ridge, Alaska

    USGS Publications Warehouse

    Marlow, M. S.; Scholl, D. W.; Buffington, E.C.; Boyce, R.E.; Alpha, T.R.; Smith, P.J.; Shipek, C.J.

    1970-01-01

    Buldir Depression is a large, rectilinear basin that lies on the northern edge of the Aleutian Ridge and is aligned with the arcuate chain of active volcanoes on the ridge crest. The depression appears to be a volcanic-tectonic feature, which began to form in Late Tertiary time and which is still forming. It is a graben formed by extensional rifting and accompanied by contemporaneous volcanism on the Aleutian Ridge. Subsidence rates for the depression are estimated at 20-70 cm/1,000 years. Sediments in the depression are 300 m thick and are probably pelagic and turbidite deposits of Pleistocene age. The turbidites were apparently derived from the plateau area of the Aleutian Ridge surrounding the depression. Older sediments on the northern slope of the Aleutian Ridge have a maximum thickness of 550 m and are deformed and slumped toward the Bering Sea. These sediments are postulated to overlie a mid-flank terrace on the northern Aleutian Ridge that titled to the north during the formation of Buldir Depression. ?? 1970.

  1. Watershed vs. within-lake drivers of nitrogen: phosphorus dynamics in shallow lakes.

    PubMed

    Ginger, Luke J; Zimmer, Kyle D; Herwig, Brian R; Hanson, Mark A; Hobbs, William O; Small, Gaston E; Cotner, James B

    2017-10-01

    Research on lake eutrophication often identifies variables affecting amounts of phosphorus (P) and nitrogen (N) in lakes, but understanding factors influencing N:P ratios is important given its influence on species composition and toxin production by cyanobacteria. We sampled 80 shallow lakes in Minnesota (USA) for three years to assess effects of watershed size, proportion of watershed as both row crop and natural area, fish biomass, and lake alternative state (turbid vs. clear) on total N : total P (TN : TP), ammonium, total dissolved phosphorus (TDP), and seston stoichiometry. We also examined N:P stoichiometry in 20 additional lakes that shifted states during the study. Last, we assessed the importance of denitrification by measuring denitrification rates in sediment cores from a subset of 34 lakes, and by measuring seston δ 15 N in four additional experimental lakes before and after they were experimentally manipulated from turbid to clear states. Results showed alternative state had the largest influence on overall N:P stoichiometry in these systems, as it had the strongest relationship with TN : TP, seston C:N:P, ammonium, and TDP. Turbid lakes had higher N at given levels of P than clear lakes, with TN and ammonium 2-fold and 1.4-fold higher in turbid lakes, respectively. In lakes that shifted states, TN was 3-fold higher in turbid lakes, while TP was only 2-fold higher, supporting the notion N is more responsive to state shifts than is P. Seston δ 15 N increased after lakes shifted to clear states, suggesting higher denitrification rates may be important for reducing N levels in clear states, and potential denitrification rates in sediment cores were among the highest recorded in the literature. Overall, our results indicate lake state was a primary driver of N:P dynamics in shallow lakes, and lakes in clear states had much lower N at a given level of P relative to turbid lakes, likely due to higher denitrification rates. Shallow lakes are often

  2. Changes in Rongbuk lake and Imja lake in the Everest region of Himalaya

    NASA Astrophysics Data System (ADS)

    Chen, W.; Doko, T.; Liu, C.; Ichinose, T.; Fukui, H.; Feng, Q.; Gou, P.

    2014-12-01

    The Himalaya holds the world record in terms of range and elevation. It is one of the most extensively glacierized regions in the world except the Polar Regions. The Himalaya is a region sensitive to climate change. Changes in the glacial regime are indicators of global climate changes. Since the second half of the last century, most Himalayan glaciers have melted due to climate change. These changes directly affected the changes of glacial lakes in the Himalayan region due to the glacier retreat. New glacial lakes are formed, and a number of them have expanded in the Everest region of the Himalayas. This paper focuses on the two glacial lakes which are Imja Lake, located at the southern slope, and Rongbuk Lake, located at the northern slope in the Mt. Everest region, Himalaya to present the spatio-temporal changes from 1976 to 2008. Topographical conditions between two lakes were different (Kruskal-Wallis test, p < 0.05). Rongbuk Lake was located at 623 m higher than Imja Lake, and radiation of Rongbuk Lake was higher than the Imja Lake. Although size of Imja Lake was larger than the Rongbuk Lake in 2008, the growth speed of Rongbuk Lake was accelerating since 2000 and exceeds Imja Lake in 2000-2008. This trend of expansion of Rongbuk Lake is anticipated to be continued in the 21st century. Rongbuk Lake would be the biggest potential risk of glacial lake outburst flood (GLOF) at the Everest region of Himalaya in the future.

  3. 78 FR 17097 - Safety Zone; Lake Havasu Triathlon; Lake Havasu City, AZ

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-03-20

    ...-AA00 Safety Zone; Lake Havasu Triathlon; Lake Havasu City, AZ AGENCY: Coast Guard, DHS. ACTION... waters of Lake Havasu and the London Bridge Channel for the Lake Havasu Triathlon. This temporary safety... participants. The waterside swim course consists of 1500 meters in Lake Havasu and the London Bridge Channel...

  4. Intraplate compressional deformation in West-Congo and the Congo basin: related to ridge-puch from the South Atlantic spreading ridge?

    NASA Astrophysics Data System (ADS)

    Delvaux, Damien; Everaerts, Michel; Kongota Isasi, Elvis; Ganza Bamulezi, Gloire

    2016-04-01

    After the break-up and separation of South America from Africa and the initiation of the South-Atlantic mid-oceanic ridge in the Albian, at about 120 Ma, ridge-push forces started to build-up in the oceanic lithosphere and were transmitted to the adjacent continental plates. This is particularly well expressed in the passive margin and continental interior of Central Africa. According to the relations of Wiens and Stein (1985) between ridge-push forces and basal drag in function of the lithospheric age of oceanic plates, the deviatoric stress reaches a compressional maximum between 50 and 100, Ma after the initiation of the spreading ridge, so broadly corresponding to the Paleocene in this case (~70-20 Ma). Earthquake focal mechanism data show that the West-Congo margin and a large part of the Congo basin are still currently under compressional stresses with an horizontal compression parallel to the direction of the active transform fracture zones. We studied the fracture network along the Congo River in Kinshasa and Brazzaville which affect Cambrian sandstones and probably also the late Cretaceous-Paleocene sediments. Their brittle tectonic evolution is compatible with the buildup of ridge-push forces related to the South-Atlantic opening. Further inland, low-angle reverse faults are found affecting Jurassic to Middle Cretaceous cores from the Samba borehole in the Congo basin and strike-slip movements are recorded as a second brittle phase in the Permian cores of the Dekese well, at the southern margin of the Congo basin. An analysis of the topography and river network of the Congo basin show the development of low-amplitude (50-100 m) long wavelengths (100-300 km) undulations that can be interpreted as lithospheric buckling in response to the compressional intraplate stress field generated by the Mid-Atlantic ridge-push. Wiens, D.A., Stein, S., 1985. Implications of oceanic intraplate seismicity for plate stresses, driving forces and theology. Tectonophysics

  5. Global Models of Ridge-Push Force, Geoid, and Lithospheric Strength of Oceanic plates

    NASA Astrophysics Data System (ADS)

    Mahatsente, Rezene

    2017-12-01

    An understanding of the transmission of ridge-push related stresses in the interior of oceanic plates is important because ridge-push force is one of the principal forces driving plate motion. Here, I assess the transmission of ridge-push related stresses in oceanic plates by comparing the magnitude of the ridge-push force to the integrated strength of oceanic plates. The strength is determined based on plate cooling and rheological models. The strength analysis includes low-temperature plasticity (LTP) in the upper mantle and assumes a range of possible tectonic conditions and rheology in the plates. The ridge-push force has been derived from the thermal state of oceanic lithosphere, seafloor depth and crustal age data. The results of modeling show that the transmission of ridge-push related stresses in oceanic plates mainly depends on rheology and predominant tectonic conditions. If a lithosphere has dry rheology, the estimated strength is higher than the ridge-push force at all ages for compressional tectonics and at old ages (>75 Ma) for extension. Therefore, under such conditions, oceanic plates may not respond to ridge-push force by intraplate deformation. Instead, the plates may transmit the ridge-push related stress in their interior. For a wet rheology, however, the strength of young lithosphere (<75 Ma) is much less than the ridge-push force for both compressional and extensional tectonics. In this case, the ridge-push related stress may dissipate in the interior of oceanic plates and diffuses by intraplate deformation. The state of stress within a plate depends on the balance of far-field and intraplate forces.

  6. How wet is wet? Strontium isotopes as paleo-lake level indicators in the Chew Bahir basin (S-Ethiopia)

    NASA Astrophysics Data System (ADS)

    Junginger, A.; Vonhof, H.; Foerster, V. E.; Asrat, A.; Cohen, A. S.; Lamb, H. F.; Schaebitz, F.; Trauth, M. H.

    2016-12-01

    A major challenge in paleo-anthropology is to understand the impact of climatic changes on human evolution. The Hominin Sites and Paleo-lakes Drilling Project (HSPDP) is currently meeting that challenge by providing records that cover the last 3.7 Ma of paleoenvironmental change all located in close proximity to key paleo-anthropological findings in East Africa. One of the cored climatic archives comes from the dried up Chew Bahir basin in southern Ethiopia, where duplicate sediment cores, each 280 m long, are expected to provide valuable insights about East African environmental variability during the last >500 ka. The lake basins in the eastern branch of the East African Rift System today contain mainly shallow and alkaline lakes. However, paleo-shorelines in the form of wave cut notches, shell beds, and beach ridges are common morphological evidences for deep freshwater lakes that have filled the basins up to their overflow level during pronounced humid episodes, such as the African Humid Period (AHP, 15-5 ka). Unfortunately, further back in time, many of those morphological features disappear due to erosion and the estimation of paleo-water depths depend merely on qualitative proxies from core analyses. We here present a new method that shows high potential to translate qualitative proxy signals from sediment core analyses to quantitative climate signals in the Ethiopian Rift. The method aims at water level reconstruction of multiple paleo-lake episodes in the Chew Bahir basin using strontium isotope ratios (87Sr/86Sr, SIR) in lacustrine fossils and microfossils. SIR preserved in lacustrine fossils reflect the lithology of the drained catchment. The catchment of Chew Bahir consists mainly of Precambrian basement rocks producing high SIR in the lake waters. During humid periods, its catchment enlarged when higher elevated paleo-lakes Abaya, Chamo and Awassa were cascading down into Chew Bahir. These basins drain mainly volcanic rocks producing low SIR. First

  7. Progressive serpentinization of the oceanic lithosphere from ridge to ridge flank: Consequences for biogeochemical cycles

    NASA Astrophysics Data System (ADS)

    Frueh-Green, G. L.; Boschi, C.

    2011-12-01

    Exposure of mantle rocks is an integral process of slow- and ultra-slow spreading ridges and ridge-flanks. Mantle-dominated lithosphere is a highly reactive chemical and thermal system, in which progressive interaction with seawater during serpentinization has significant geophysical, geochemical and biological consequences for the global marine system. This presentation is intended to provide an overview of serpentinization processes as fundamental to understanding the evolution of oceanic lithosphere formed at slow spreading ridges, fluid flow and the consequences of serpentinization for biogeochemical cycles. Seawater progressively reacts with peridotite, commonly as detachment faults unroof mantle material to the seafloor and serpentinites become dominant components of the ridge flanks. The mineral assemblages and textures of abyssal serpentinites typically record progressive, static hydration reactions that take place under a wide range of temperatures, lithospheric depths, fluid compositions and redox conditions. The products and sequence of serpentinization reactions are influenced by the time-integrated flux of seawater, bulk protolith compositions, the presence or absence of magmatic intrusions and/or trapped gabbroic melts, and structure (e.g., detachment faults, cataclastic fault zones). In turn, these factors influence mineral assemblages, fluid chemistry, and volatile contents. Serpentinization processes have major consequences for long-term, global geochemical fluxes by acting as a sink for H2O, Cl, B, U, S, and C from seawater and a source of Ca, Ni and possibly Cr to hydrothermal fluids, and by producing hydrogen-rich reduced fluids that are critical to sustain microbial communities. Seafloor weathering of serpentinized abyssal peridotites may also result in Mg loss and enhanced B uptake during clay mineral formation. The production of hydrogen during serpentinization is generally attributed to the formation of magnetite during olivine hydration and

  8. Competition between larval lake herring (Coregonus artedi) and lake whitefish (Coregonus clupeaformis) for zooplankton

    USGS Publications Warehouse

    Davis, Bruce M.; Todd, Thomas N.

    1998-01-01

    Diet and growth of larval lake herring (Coregonus artedi) and lake whitefish (Coregonus clupeaformis) were compared in mesocosm experiments in a small mesotrophic lake in southeastern Michigan. Fish were sampled from single-species and mixed assemblages in 2-m3 cages for 8 weeks during April and May. Both species initially ate mostly cyclopoid copepodites and small cladocerans (Bosmia spp.). Schoener's index of diet overlap showed considerable overlap (70-90%). Lake whitefish ate Daphnia spp. and adult copepods about 2 weeks earlier than did lake herring, perhaps related to their larger mean mouth gape. Lake whitefish were consistently larger than lake herring until the eighth week, especially in the sympatric treatments. Lake whitefish appeared to have a negative effect on the growth of lake herring, as lake herring in mixed-species treatments were smaller and weighed less than lake herring reared in single-species treatments. The diet similarities of lake whitefish and lake herring larvae could make them competitors for food in the Great Lakes. The greater initial size of lake whitefish could allow them to eat larger prey earlier and thereby limit availability of these prey to lake herring at a crucial period of development.

  9. Late Noachian and early Hesperian ridge systems in the south circumpolar Dorsa Argentea Formation, Mars: Evidence for two stages of melting of an extensive late Noachian ice sheet

    NASA Astrophysics Data System (ADS)

    Kress, Ailish M.; Head, James W.

    2015-05-01

    -based glaciation. The Late Noachian and Early Hesperian ages of the ridge systems closely correspond to the ages of valley network/open basin lake systems, representing runoff, drainage and storage of liquid water in non-polar regions of the surface of Mars. Potential causes of such wet-based conditions in the DAF include: 1) top-down melting due to atmospheric warming, 2) enhanced snow and ice accumulation and raising of the melting isotherm to the base of the ice sheet, or 3) basal melting associated with intrusive volcanism (volcano-ice interactions). The early phase of melting is closely correlated in time with valley network formation and thus may be due to global atmospheric warming, while the later phase of melting may be linked to Early Hesperian global volcanism and specific volcano-ice interactions (table mountains) in the DAF. Crater ages indicate that these wet-based conditions ceased by the Late Hesperian, and that further retreat of the DAF to its present configuration occurred largely through sublimation, not melting, thus preserving the extensive ridge systems. MARSIS radar data suggest that significant areas of layered, potentially ice-rich parts of the Dorsa Argentea Formation remain today.

  10. The Morphometry of Lake Palmas, a Deep Natural Lake in Brazil

    PubMed Central

    Barroso, Gilberto F.; Gonçalves, Monica A.; Garcia, Fábio da C.

    2014-01-01

    Lake Palmas (A = 10.3km2) is located in the Lower Doce River Valley (LDRV), on the southeastern coast of Brazil. The Lake District of the LDRV includes 90 lakes, whose basic geomorphology is associated with the alluvial valleys of the Barreiras Formation (Cenozoic, Neogene) and with the Holocene coastal plain. This study aimed to investigate the relationship of morphometry and thermal pattern of a LDRV deep lake, Lake Palmas. A bathymetric survey carried out in 2011 and the analysis of hydrographic and wind data with a geographic information system allowed the calculation of several metrics of lake morphometry. The vertical profiling of physical and chemical variables in the water column during the wet/warm and dry/mild cold seasons of 2011 to 2013 has furnished a better understanding of the influence of the lake morphometry on its structure and function. The overdeepened basin has a subrectangular elongated shape and is aligned in a NW-SE direction in an alluvial valley with a maximum depth (Zmax) of 50.7m, a volume of 2.2×108 m3 (0.22km3) and a mean depth (Zmv) of 21.4m. These metrics suggest Lake Palmas as the deepest natural lake in Brazil. Water column profiling has indicated strong physical and chemical stratification during the wet/warm season, with a hypoxic/anoxic layer occupying one-half of the lake volume. The warm monomictic pattern of Lake Palmas, which is in an accordance to deep tropical lakes, is determined by water column mixing during the dry and mild cold season, especially under the influence of a high effective fetch associated with the incidence of cold fronts. Lake Palmas has a very long theoretical retention time, with a mean of 19.4 years. The changes observed in the hydrological flows of the tributary rivers may disturb the ecological resilience of Lake Palmas. PMID:25406062

  11. Embryotoxicity of Great Lakes lake trout extracts to developing rainbow trout

    USGS Publications Warehouse

    Wright, Peggy J.; Tillitt, Donald E.

    1999-01-01

    Planar halogenated hydrocarbons (PHHs), such as polychlorinated dibenzo-p-dioxins, dibenzofurans, and biphenyls are present in aquatic systems, and are known to produce adverse effects in fish. This study investigated the embryotoxicity of PHH mixtures through the nanoinjection of environmental extracts into newly fertilized eggs from two strains of rainbow trout. Organic extracts were obtained from whole adult lake trout collected from Lake Michigan in 1988 and Lake Superior in 1994. The graded doses of the final extracts used for injection were quantified as 2,3,7,8-tetrachlorodibenzo-p-dioxin toxic-equivalents (TEQs) based on the concentrations of dioxins, furans and non-o-PCBs in each, and as equivalent amounts found in the eggs of the original lake trout (eggEQ). Total TEQs in the lake trout were 14.7 pg TEQ/g in the Lake Michigan sample and 7.3 pg TEQ/g in the Lake Superior sample. The extract of the Lake Michigan lake trout was embryotoxic to rainbow trout; LD50 values were 35 eggEQ (15–90, 95% F.L.) in the Arlee strain and 14 eggEQ (5–99, 95% F.L.) in the Erwin strain of rainbow trout. The LD50 values of the Lake Michigan extract in either of these strains of rainbow trout fall within the actual range of TCDD LD50values based on TEQs. This indicates that an additive model of toxicity is appropriate to quantify PHHs in relation to early life stage mortality in fish. Gross lesions characteristic of exposure to PHHs (i.e. yolk-sac edema, craniofacial deformities, and hemorrhaging) increased in a dose-related manner. The lowest observable adverse effect concentrations (LOAEC) for these gross lesions and cumulative mortalities suggests that current concentrations of PHHs in lake trout from Lake Michigan are above a threshold for adverse effects and these compounds may have implications on the lack of recruitment in certain Great Lakes lake trout populations.

  12. Great Lakes

    NASA Image and Video Library

    2017-12-08

    Bands of lake effect snow drift eastward from the western Great Lakes in this true-color image captured by the NOAA/NASA Suomi NPP satellite's Visible Infrared Imaging Radiometer Suite (VIIRS) instrument on January 5, 2017. National Weather Service forecasters expect light to moderate lake effect snow showers to continue throughout the day today and into Saturday (1/7). Lake-effect snow forms when cold air passes over the warmer waters of a lake. This causes some lake water to evaporate into the air and warm it. This warmer, wetter air rises and cools as it moves away from the lake. When it cools, it releases that moisture and, if it’s cold enough, that moisture turns into snow. Although true-color images like this may appear to be photographs of Earth, they aren't. They are created by combining data from the three color channels on the VIIRS instrument sensitive to the red, green and blue (or RGB) wavelengths of light into one composite image. In addition, data from several other channels are often also included to cancel out or correct atmospheric interference that may blur parts of the image. Credit: NOAA/NASA/Suomi NPP via NOAA's Environmental Visualization Laboratory

  13. Lake Michigan lake trout PCB model forecast post audit

    EPA Science Inventory

    Scenario forecasts for total PCBs in Lake Michigan (LM) lake trout were conducted using the linked LM2-Toxics and LM Food Chain models, supported by a suite of additional LM models. Efforts were conducted under the Lake Michigan Mass Balance Study and the post audit represents th...

  14. 60 Years of Great Science (Oak Ridge National Laboratory)

    DOE R&D Accomplishments Database

    2003-01-01

    This issue of Oak Ridge National Laboratory Review (vol. 36, issue 1) highlights Oak Ridge National Laboratory's contributions in more than 30 areas of research and related activities during the past 60 years and provides glimpses of current activities that are carrying on this heritage.

  15. Community-Wide Education Outreach for the Ridge2000 Research Program

    NASA Astrophysics Data System (ADS)

    Goehring, E.

    2004-12-01

    Ridge2000 is a multidisciplinary NSF sponsored research initiative to explore Earth's spreading ridge system as an integrated whole. The Ridge2000 community is comprised of scientists from universities and research institutions across the country. Building on existing exemplary outreach efforts (e.g., REVEL, Dive&Discover, Volcanoes of the Deep Sea IMAX), Ridge2000 education outreach has begun to develop community-wide education offerings - programs to which Ridge2000 scientists and others may contribute. Community-wide efforts offer the advantages of serving larger audiences of scientists as well as educators and students and providing avenues for scientists interested in education outreach but with limited time or experience. Coordination of researchers' educational efforts also better leverages the resources of the funding agency - NSF. Here we discuss an exciting Ridge2000 pilot program called SEAS - Student Experiments At Sea. SEAS is a web-based program for middle and high school students to learn science by doing science. SEAS students study the exciting, relatively unexplored world of hydrothermal vents and learn to ask questions about this environment just as researchers do. SEAS goes beyond "follow-along" outreach by inviting students to participate in research through formal proposal and report competitions. The program was concept-tested during the 2003-2004 academic year, with 14 pilot teachers and approximately 800 students. Five student experiments were conducted at sea, with data posted to the website during the cruise. Student reports as well as scientist comments are posted there as well (http://www.ridge2000.org/SEAS/). It was an exciting year! Over 20 Ridge2000 scientists contributed their time and expertise to the SEAS program in its first year. Scientists are invited to contribute in a variety of ways, all of which help satisfy the requirement's of NSF's Broader Impacts Criterion. They may help develop curriculum topics, consult on

  16. Formation and Elimination of Transform Faults on the Reykjanes Ridge

    NASA Astrophysics Data System (ADS)

    Martinez, Fernando; Hey, Richard

    2017-04-01

    The Reykjanes Ridge is a type-setting for examining processes that form and eliminate transform faults because it has undergone these events systematically within the Iceland gradient in hot-spot influence. A Paleogene change in plate motion led to the abrupt segmentation of the originally linear axis into a stair-step ridge-transform configuration. Its subsequent evolution diachronously and systematically eliminated the just-formed offsets re-establishing the original linear geometry of the ridge over the mantle, although now spreading obliquely. During segmented stages accreted crust was thinner and during unsegmented stages southward pointing V-shaped crustal ridges formed. Although mantle plume effects have been invoked to explain the changes in segmentation and crustal features, we propose that plate boundary processes can account for these changes [Martinez & Hey, EPSL, 2017]. Fragmentation of the axis was a mechanical effect of an abrupt change in plate opening direction, as observed in other areas, and did not require mantle plume temperature changes. Reassembly of the fragmented axis to its original linear configuration was controlled by a deep damp melting regime that persisted in a linear configuration following the abrupt change in opening direction. Whereas the shallow and stronger mantle of the dry melting regime broke up into a segmented plate boundary, the persistent deep linear damp melting regime guided reassembly of the ridge axis back to its original configuration by inducing asymmetric spreading of individual ridge segments. Effects of segmentation on mantle upwelling explain crustal thickness changes between segmented and unsegmented phases of spreading without mantle temperature changes. Buoyant upwelling instabilities propagate along the long linear deep melting regime driven by regional gradients in mantle properties away from Iceland. Once segmentation is eliminated, these propagating upwelling instabilities lead to crustal thickness

  17. Water-quality and lake-stage data for Wisconsin lakes, water year 2005

    USGS Publications Warehouse

    Rose, W.J.; Garn, H.S.; Goddard, G.L.; Marsh, S.B.; Olson, D.L.; Robertson, Dale M.

    2006-01-01

    The U.S. Geological Survey (USGS), in cooperation with local and other agencies, collects data at selected lakes throughout Wisconsin. These data, accumulated over many years, provide a data base for developing an improved understanding of the water quality of lakes. The purpose of this report is to provide information about the chemical and physical charac-teristics of Wisconsin lakes. Data that have been collected at specific lakes, and information to aid in the interpretation of those data, are included in this report. Data collected include measure-ments of in-lake water quality and lake stage. Time series graphs of Secchi depths, surface total phosphorus and chlorophyll a concentrations collected during non-frozen periods are included for all lakes. Graphs of vertical profiles of temperature, dissolved oxygen, pH, and specific conductance are included for sites where these parameters were measured. Descriptive infor-mation for each lake includes: location of the lake, area of the lake's watershed, period for which data are available, revisions to previously published records, and pertinent remarks.

  18. The Effects of Aseismic Ridge Collision on Upper Plate Deformation: Cocos Ridge Collision and Deformation of the Western Caribbean

    NASA Astrophysics Data System (ADS)

    La Femina, P. C.; Govers, R. M. A.; Ruiz, G.; Geirsson, H.; Camacho, E.; Mora-Paez, H.

    2015-12-01

    The collision of the Panamanian isthmus with northwestern South America is thought to have initiated as early as Oligocene - Miocene time (23-25 Ma) based on geologic and geophysical data and paleogeographic reconstructions. This collision was driven by eastward-directed subduction beneath northwestern South America. Cocos - Caribbean convergence along the Middle America Trench, and Nazca - Caribbean oblique convergence along the South Panama Deformed Belt have resulted in complex deformation of the southwestern Caribbean since Miocene - Pliocene time. Subduction and collision of the aseismic Cocos Ridge is thought to have initiated <3.5 Ma and has been linked to: 1) late Miocene-Pliocene cessation of volcanism and uplift of the Cordillera de Talamanca, Costa Rica; 2) Quaternary migration of the volcanic arc toward the back-arc in Costa Rica; 3) Quaternary to present deformation within the Central Costa Rica Deformed Belt; 4) Quaternary to present shortening across the fore-arc Fila Costeña fold and thrust belt and back-arc North Panama Deformed Belt (NPDB); 5) Quaternary to present outer fore-arc uplift of Nicoya Peninsula above the seamount domain, and the Osa and Burica peninsulas above the ridge; and 6) Pleistocene to present northwestward motion of the Central American Fore Arc (CAFA) and northeastward motion of the Panama Region. We investigate the geodynamic effects of Cocos Ridge collision on motion of the Panama Region with a new geodynamic model. The model is compared to a new 1993-2015 GPS-derived three-dimensional velocity field for the western Caribbean and northwestern South America. Specifically, we test the hypotheses that the Cocos Ridge is the main driver for upper plate deformation in the western Caribbean. Our models indicate that Cocos Ridge collision drives northwest-directed motion of the CAFA and the northeast-directed motion of the Panama Region. The Panama Region is driven into the Caribbean across the NPDB and into northwestern South

  19. Using Satellite Imagery to Monitor the Major Lakes; Case Study Lake Hamun

    NASA Astrophysics Data System (ADS)

    Norouzi, H.; Islam, R.; Bah, A.; AghaKouchak, A.

    2015-12-01

    Proper lakes function can ease the impact of floods and drought especially in arid and semi-arid regions. They are important environmentally and can directly affect human lives. Better understanding of the effect of climate change and human-driven changes on lakes would provide invaluable information for policy-makers and local people. As part of a comprehensive study, we aim to monitor the land-cover/ land-use changes in the world's major lakes using satellite observations. As a case study, Hamun Lake which is a pluvial Lake, also known as shallow Lake, located on the south-east of Iran and adjacent to Afghanistan, and Pakistan borders is investigated. The Lake is the main source of resources (agriculture, fishing and hunting) for the people around it and politically important in the region since it is shared among three different countries. The purpose of the research is to find the Lake's area from 1972 to 2015 and to see if any drought or water resources management has affected the lake. Analyzing satellites imagery from Landsat shows that the area of the Lake changes seasonally and intra-annually. Significant seasonal effects are found in 1975,1977, 1987, 1993, 1996, 1998, 2000, 2009 and 2011, as well as, substantial amount of shallow water is found throughout the years. The precipitation records as well as drought historical records are studied for the lake's basin. Meteorological studies suggest that the drought, decrease of rainfalls in the province and the improper management of the Lake have caused environmental, economic and geographical consequences. The results reveal that lake has experienced at least two prolong dryings since 1972 which drought cannot solely be blamed as main forcing factor.Proper lakes function can ease the impact of floods and drought especially in arid and semi-arid regions. They are important environmentally and can directly affect human lives. Better understanding of the effect of climate change and human-driven changes on lakes

  20. A coupled lake-atmosphere model (CLAM) and its application to Lake Kinneret

    NASA Astrophysics Data System (ADS)

    Pan, Hai

    1999-08-01

    Kinneret is a 166-km2 lake located in Northern Israel, in the central part of the Jordan Valley, a corridor running from north to south, between the Galilee hills in the west and the Golan Heights in the east. Both the Galilee hills and the Golan Heights reach an elevation of about 400 m above mean sea level (MSL), and the lake is about -210 m (MSL). North of the lake is the mountainous area of the Hermon, culminating at about 2800 m (MSL). About 120 km south of it is the Dead Sea, which is about -410 m (MSL), and about 45 km west of it is the Mediterranean Sea. The complexity of the terrain, combined with relatively arid soil and various ground covers surrounding the lake, results in a very complicated system of atmospheric and lake processes. To understand this system, especially the processes affecting the atmosphere and lake dynamics and thermodynamics, and their effects on Lake Kinneret evaporation, a coupled lake-atmosphere model (CLAM) was developed and applied to the lake region. The CLAM is based on the Regional Atmospheric Modeling System (RAMS) and the oceanic S-coordinate Rutgers University Model (SCRUM). Energy, mass, and momentum are conserved at the interface between the atmosphere and the lake, and appropriate balance equations are applied there. In the atmospheric module, two nested grids are employed to simulate Northern Israel at a resolution of 4 x 4 km2, and the near-lake region at a resolution of 1 x 1 km 2. Synoptic conditions obtained from the National Meteorological Center (NMC) reanalysis are assimilated by the model. Soil moisture, which appears to have a significant impact on atmospheric circulation in this region, was transformed from the normalized difference vegetation index (NDVI). Observations collected during two summers above and inside the lake emphasize the good capability of CLAM to simulate surface fluxes and other microclimatic conditions, as well as lake temperature and currents. Although the lake is small (about 12-km wide

  1. East Pacific Rise at lat 19°S: Evidence for a recent ridge jump

    NASA Astrophysics Data System (ADS)

    Morton, Janet L.; Ballard, Robert D.

    1986-02-01

    A detailed ANGUS (Acoustically Navigated Geological Undersea Surveyor) photographic and bathymetric survey of the East Pacific Rise (EPR) near lat 19°S reveals a small jump of the ridge axis to the west. The axial block in this region consists of two parallel ridges 3 km apart and separated by a 200-m-deep valley. South of lat 19°06‧S the plate boundary is a single, narrow (<1 km) ridge. The eastern ridge near lat 19°S is shallower than the western ridge and is morphologically a continuation of the narrow, active ridge axis to the south. ANGUS photographs along both ridges and in the intervening valley, however, show that the western ridge is the currently active plate boundary. We suggest that spreading shifted westward from the eastern ridge to its present position within the past 40 000 yr. The EPR in the general region has been characterized by asymmetric spreading for the past 2.4 m.y. The sense of the ridge jump near lat 19°S is consistent with the asymmetric spreading, which could have been produced by a series of such jumps.

  2. Bathymetric Surveys of Lake Arthur and Raccoon Lake, Pennsylvania, June 2007

    USGS Publications Warehouse

    Hittle, Clinton D.; Ruby, A. Thomas

    2008-01-01

    In spring of 2007, bathymetric surveys of two Pennsylvania State Park lakes were performed to collect accurate data sets of lake-bed elevations and to develop methods and techniques to conduct similar surveys across the state. The lake-bed elevations and associated geographical position data can be merged with land-surface elevations acquired through Light Detection and Ranging (LIDAR) techniques. Lake Arthur in Butler County and Raccoon Lake in Beaver County were selected for this initial data-collection activity. In order to establish accurate water-surface elevations during the surveys, benchmarks referenced to NAVD 88 were established on land at each lake by use of differential global positioning system (DGPS) surveys. Bathymetric data were collected using a single beam, 210 kilohertz (kHz) echo sounder and were coupled with the DGPS position data utilizing a computer software package. Transects of depth data were acquired at predetermined intervals on each lake, and the shoreline was delineated using a laser range finder and compass module. Final X, Y, Z coordinates of the geographic positions and lake-bed elevations were referenced to NAD 83 and NAVD 88 and are available to create bathymetric maps of the lakes.

  3. Sedimentary and structural patterns on the northern Santa Rosa-Cortes Ridge, southern California

    USGS Publications Warehouse

    Field, M.E.; Richmond, W.C.

    1980-01-01

    The Santa Rosa-Cortes Ridge is an 1800 m high, 180 km long feature lying approximately 90 km off the coast of southern California and directly south of the northern group of Channel Islands. Geophysical profiling and sampling cruises to the northern part of the ridge, an area of recent and future lease sales for petroleum development, provide a strong data base for interpretation of structural and sedimentary patterns and their relation to potential geologic hazards. The northern part of the ridge is a complexly folded and faulted northwest-trending anticlinorium composed mostly of lower and middle Miocene shale and mudstone. Erosional remnants of upper Miocene and Pliocene rocks unconformably overlie highly folded pre-upper Miocene strata. The major structure of the ridge developed almost continuously from Oligocene or early Miocene time to the end of the Tertiary; many small folds formed between post-late Miocene and pre-late Pleistocene time. Numerous small faults cut the rocks on the ridge top. Faults cut basement rocks on the west side of the ridge along the Ferrelo fault zone. Published data on historical epicenters and evidence of offsets on the seafloor from seismic reflection and side-scan profiles, including limited evidence of possible strike-slip movement along fault traces, indicate that the northern Santa Rosa-Cortes Ridge is tectonically active. The crest of the ridge was truncated as the result of repeated sea-level fluctuations in the Quaternary. A thin veneer of unconsolidated medium to fine sand, less than 3 m thick, mantles most of the ridge; locally in topographically low areas and on the upper flanks of the ridge, thickness exceeds 20 m. The meager sediment cover, coupled with available evidence of relatively strong currents flowing across the ridge top, indicate that the ridge is an area of nondeposition or winnowing of fine sediments. Modern sediments become thicker and finer-grained from the ridge top to the ridge flanks, suggesting active

  4. Magnetic Anomalies over the Mid-Atlantic Ridge near 27{degrees}N.

    PubMed

    Phillips, J D

    1967-08-25

    Ten magnetic profiles across the mid-Atlantic ridge near 27 degrees N show trends that are parallel to the ridge axis and symmetrical about the ridge axis. The configuration of magnetic bodies that could account for the pattern supports the Vine and Matthews hypothesis for the origin of magnetic anomalies over oceanic ridges. A polarity-reversal time scale inferred from models for sea-floor spreading in the Pacific-Antarctic ridge and radiometrically dated reversals of the geomagnetic field indicates a spreading rate of 1.25 centimeters per year during the last 6 million years and a rate of 1.65 centimeters per year between 6 and 10 million years ago. A similar analysis of more limited data over the mid-Atlantic ridge near 22 degrees N also indicates a change in the spreading rate. Here a rate of 1.4 centimeters per year appears to have been in effect during the last 5 million years; between 5 and 9 million years ago, an increased rate of 1.7 centimeters per year is indicated. The time of occurrence and relative magnitude of these changes in the spreading rate, about 5 to 6 million years ago and 18 to 27 percent, respectively, accords with the spreading rate change implied for the Juan de Fuca ridge in the northeast Pacific.

  5. The Sagatu Ridge dike swarm, Ethiopian rift margin. [tectonic evolution

    NASA Technical Reports Server (NTRS)

    Mohr, P. A.; Potter, E. C.

    1976-01-01

    A swarm of dikes forms the core of the Sagatu Ridge, a 70-km-long topographic feature elevated to more than 4000 m above sea level and 1500 m above the level of the Eastern (Somalian) plateau. The ridge trends NNE and lies about 50 km east of the northeasterly trending rift-valley margin. Intrusion of the dikes and buildup of the flood-lava pile, largely hawaiitic but with trachyte preponderant in the final stages, occurred during the late Pliocene-early Pleistocene and may have been contemporaneous with downwarping of the protorift trough to the west. The ensuing faulting that formed the present rift margin, however, bypassed the ridge. The peculiar situation and orientation of the Sagatu Ridge, and its temporary existence as a line of crustal extension and voluminous magmatism, are considered related to a powerful structural control by a major line of Precambrian crustal weakness, well exposed further south. Transverse rift structures of unknown type appear to have limited the development of the ridge to the north and south.

  6. STS-42 Earth observation of the Rhone River / Lake Geneva in Switzerland

    NASA Technical Reports Server (NTRS)

    1992-01-01

    STS-42 Earth observation taken aboard Discovery, Orbiter Vehicle (OV) 103, shows the Rhone River flowing into Lake Geneva in western Switzerland (46.0N, 7.0E). The sharp change in the valley's orientation is a feature of this view. Several times during cold periods of the Earth's history (the geologically recent Ice Ages of the last 1.5 million years or so), this valley has been filled with ice flowing off the mountain ranges. Ice erosion has widened and lowered the valley. The surrounding mountain chains include the highest peak in Europe, Mont Blanc (15,781 feet) on the French-Italian border, and the well-known Matterhorn (14,130) feet on the Swiss-Italian border. Ice-sculpting has generated the characteristically sharp ridges and pointed peaks of the Alps.

  7. Comparison of catch and lake trout bycatch in commercial trap nets and gill nets targeting lake whitefish in northern Lake Huron

    USGS Publications Warehouse

    Johnson, James E.; Ebener, Mark P.; Gebhardt, Kenneth; Bergstedt, Roger

    2004-01-01

    We compared seasonal lake whitefish catch rates, lake trout bycatch, and gearinduced lake trout mortality between commercial trap nets and gill nets in north-central Lake Huron. Onboard monitors recorded catches from 260 gill net and 96 trap net lifts from October 1998 through December 1999. Catch rates for lake whitefish were highest in fall for both gear types, reflecting proximity of spawning sites to the study area. Lake whitefish catch rates were also relatively high in spring but low in both gear types in summer. Lake trout were the principal bycatch species in both gears. The lake trout bycatch was lowest in both gear types in fall, highest in gill nets in spring, and highest in trap nets in summer. The ratio of lake trout to legal whitefish (the target species) was highest in summer and lowest in fall in both gear types. The high lake trout ratio in summer was due principally to low catch rates of lake whitefish. All but 3 of 186 live lake trout removed from trap net pots survived for at least two days of observation in laboratory tanks. Therefore, we estimated that post-release survival of trap netted lake trout that had not been entangled in the mesh was 98.4%. In addition, we accounted for stress-induced mortality for lake trout that were live at capture but entangled in the mesh of either gear type. Resulting estimates of lake trout survival were higher in trap nets (87.8%) than in gill nets (39.6%). The number of lake trout killed per lift was highest during summer in trap nets and during spring in gill nets. In trap nets, 85% of dead lake trout were observed to be entangled in the mesh of the pot or tunnels. Survival rates of lake trout in gill nets were higher in our study than reported by others, probably because our nets were hand lifted in a small boat. Our trap net-induced mortality estimates on lake trout were higher than those reported by others because we adjusted our estimates to account for post-release mortality caused by handling and

  8. Lake levels, streamflow, and surface-water quality in the Devils Lake area, North Dakota

    USGS Publications Warehouse

    Wiche, Gregg J.

    1996-01-01

    The Devils Lake Basin is a 3,810-square-mile (mi2) closed basin (fig. 1) in the Red River of the North Basin. About 3,320 mi2 of the total 3,810 mi2 is tributary to Devils Lake; the remainder is tributary to Stump Lake.Since glaciation, the lake level of Devils Lake has fluctuated from about 1,457 feet (ft) above sea level (asl), the natural spill elevation of the lake to the Sheyenne River, to 1,400 ft asl (Aronow, 1957). Although no documented records of lake levels are available before 1867, Upham (1895, p. 595), on the basis of tree-ring chronology, indicated that the lake level was 1,441 ft asl in 1830. Lake levels were recorded sporadically from 1867 to 1901 when the U.S. Geological Survey established a gaging station on Devils Lake. From 1867 to the present (1996), the lake level has fluctuated between a maximum of 1,438.4 ft asl in 1867 and a minimum of 1,400.9 ft asl in 1940 (fig. 2). On July 31, 1996, the lake level was 1,437.8 ft asl, about 15.2 ft higher than the level recorded in February 1993 and the highest level in about 120 years.Since 1993, the lake level of Devils Lake (fig. 2) has risen rapidly in response to above-normal precipitation from the summer of 1993 to the present, and 30,000 acres of land around the lake have been flooded. The above-normal precipitation also has caused flooding elsewhere in the Devils Lake Basin. State highways near Devils Lake are being raised, and some local roads have been closed because of flooding.In response to the flooding, the Devils Lake Basin Interagency Task Force, comprised of many State and Federal agencies, was formed in 1995 to find and propose intermediate (5 years or less) solutions to reduce the effects of high lake levels. In addition to various planning studies being conducted by Federal agencies, the North Dakota State Water Commission has implemented a project to store water on small tracts of land and in the chain of lakes (Sweetwater Lake, Morrison Lake, Dry Lake, Mikes Lake, Chain Lake

  9. Genetic diversity of Diporeia in the Great Lakes: comparison of Lake Superior to the other Great Lakes

    EPA Science Inventory

    Abundances of Diporeia have dropped drastically in the Great Lakes, except in Lake Superior, where data suggest that population counts actually have risen. Various ecological, environmental, or geographic hypotheses have been proposed to explain the greater abundance of Lake Supe...

  10. Water-quality and lake-stage data for Wisconsin lakes, water year 1996

    USGS Publications Warehouse

    ,

    1997-01-01

    The purpose of this report is to provide information about the physical and chemical characteristics of Wisconsin lakes. Data that have been collected at specific lakes, and information to aid in the interpretation of those data, are included in this report. Data collected includes measurements of lake stage and in-lake water quality. Graphs of Secchi depths, surface totalphosphorus and chlorophyll-a concentrations versus time are included for lakes with two or more years of data. Graphs of vertical profiles of temperature, dissolved oxygen, pH, and specific conductance are included for sites where these parameters were measured. Descriptive information for each lake includes: location of the lake, drainage area of the lake's watershed, period for which data are available, revisions to previously published records, and pertinent remarks. Additional data, such as streamflow and water quality in tributary and outlet streams of some of the lakes, are published in another volume: "Water Resources Data-Wisconsin, 1996."

  11. Extraction of lead and ridge characteristics from SAR images of sea ice

    NASA Technical Reports Server (NTRS)

    Vesecky, John F.; Smith, Martha P.; Samadani, Ramin

    1990-01-01

    Image-processing techniques for extracting the characteristics of lead and pressure ridge features in SAR images of sea ice are reported. The methods are applied to a SAR image of the Beaufort Sea collected from the Seasat satellite on October 3, 1978. Estimates of lead and ridge statistics are made, e.g., lead and ridge density (number of lead or ridge pixels per unit area of image) and the distribution of lead area and orientation as well as ridge length and orientation. The information derived is useful in both ice science and polar operations for such applications as albedo and heat and momentum transfer estimates, as well as ship routing and offshore engineering.

  12. Mid-ocean-ridge seismicity reveals extreme types of ocean lithosphere.

    PubMed

    Schlindwein, Vera; Schmid, Florian

    2016-07-14

    Along ultraslow-spreading ridges, where oceanic tectonic plates drift very slowly apart, conductive cooling is thought to limit mantle melting and melt production has been inferred to be highly discontinuous. Along such spreading centres, long ridge sections without any igneous crust alternate with magmatic sections that host massive volcanoes capable of strong earthquakes. Hence melt supply, lithospheric composition and tectonic structure seem to vary considerably along the axis of the slowest-spreading ridges. However, owing to the lack of seismic data, the lithospheric structure of ultraslow ridges is poorly constrained. Here we describe the structure and accretion modes of two end-member types of oceanic lithosphere using a detailed seismicity survey along 390 kilometres of ultraslow-spreading ridge axis. We observe that amagmatic sections lack shallow seismicity in the upper 15 kilometres of the lithosphere, but unusually contain earthquakes down to depths of 35 kilometres. This observation implies a cold, thick lithosphere, with an upper aseismic zone that probably reflects substantial serpentinization. We find that regions of magmatic lithosphere thin dramatically under volcanic centres, and infer that the resulting topography of the lithosphere-asthenosphere boundary could allow along-axis melt flow, explaining the uneven crustal production at ultraslow-spreading ridges. The seismicity data indicate that alteration in ocean lithosphere may reach far deeper than previously thought, with important implications towards seafloor deformation and fluid circulation.

  13. A seismically active section of the Southwest Indian Ridge

    NASA Astrophysics Data System (ADS)

    Wald, David J.; Wallace, Terry C.

    1986-10-01

    The section of the Southwest Indian Ocean Ridge west of the Prince Edward Fracture zone has a large ridge axis offset and a complicated ridge-transform morphology. We have determined the source mechanisms of transform earthquakes along this portion of the ridge from an inversion of long-period P and SH waveforms. The seismicity is characterized by anomalous faulting mechanisms, source complexity and an unexpectedly large seismic moment release. Several earthquakes with dip-slip components of faulting have been recognized on the central section of the Andrew Bain and 32° E transforms suggesting geometrical complexity along the transform. This region has experienced a Mw = 8.0 transform earthquake in 1942, yet we observe a seismic slip rate during the last 20 years that is still comparable to the predicted spreading rate (1.6 cm/yr). The calculated slip rate over a period of 60 years is three times greater than the expected rate of spreading.

  14. Wrinkle ridges in the floor material of Kasei Valles, Mars: Nature and origin

    NASA Technical Reports Server (NTRS)

    Watters, Thomas R.; Craddock, Robert A.

    1991-01-01

    Wrinkle ridges on Mars occur almost exclusively in smooth plains material referred to as ridged plains. One of the largest contiguous units of ridged plains occurs on Lunae Planum on the eastern flank of the Tharsis rise. The eastern, western, and northern margins of the ridged plains of Lunae Planum suffered extensive erosion in early Amazonian channel-forming events. The most dramatic example of erosion in early Amazonian plains is in Kasei Valles. The nature an origin of the wrinkle ridges in the floor material of Kasei Valles are discussed.

  15. 75 FR 20859 - Temporary Concession Contract for Blue Ridge Parkway, NC/VA

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-04-21

    ... DEPARTMENT OF THE INTERIOR National Park Service Temporary Concession Contract for Blue Ridge... of temporary concession contract for Blue Ridge Parkway. SUMMARY: Pursuant to 36 CFR 51.24, public... for the conduct of certain visitor services within Blue Ridge Parkway, North Carolina and Virginia for...

  16. Delineation of sympatric morphotypes of lake trout in Lake Superior

    USGS Publications Warehouse

    Moore, Seth A.; Bronte, Charles R.

    2001-01-01

    Three morphotypes of lake trout Salvelinus namaycush are recognized in Lake Superior: lean, siscowet, and humper. Absolute morphotype assignment can be difficult. We used a size-free, whole-body morphometric analysis (truss protocol) to determine whether differences in body shape existed among lake trout morphotypes. Our results showed discrimination where traditional morphometric characters and meristic measurements failed to detect differences. Principal components analysis revealed some separation of all three morphotypes based on head and caudal peduncle shape, but it also indicated considerable overlap in score values. Humper lake trout have smaller caudal peduncle widths to head length and depth characters than do lean or siscowet lake trout. Lean lake trout had larger head measures to caudal widths, whereas siscowet had higher caudal peduncle to head measures. Backward stepwise discriminant function analysis retained two head measures, three midbody measures, and four caudal peduncle measures; correct classification rates when using these variables were 83% for leans, 80% for siscowets, and 83% for humpers, which suggests the measures we used for initial classification were consistent. Although clear ecological reasons for these differences are not readily apparent, patterns in misclassification rates may be consistent with evolutionary hypotheses for lake trout within the Laurentian Great Lakes.

  17. Submarine sand ridges and sand waves in the eastern part of the China Sea

    NASA Astrophysics Data System (ADS)

    Wu, Ziyin; Li, Shoujun; Shang, Jihong; Zhou, Jieqiong; Zhao, Dineng; Liang, Yuyang

    2016-04-01

    Integrated with multi-beam and single-beam echo sounding data, as well as historical bathymetric data, submarine bathymetric maps of the eastern part of the China Sea, including the Bohai Sea, Huanghai Sea, and East China Sea, are constructed to systematically study submarine sand ridges and sand waves in the eastern part of the China Sea, combined with high-resolution seismic, sub-bottom profile and borehole data. Submarine sand ridges are extraordinarily developed in the eastern part of the China Sea, and 7 sand ridge areas can be divided from north to south, that is, the Laotieshan Channel sand ridge area in the Bohai Sea, the Korea Bay sand ridge area in the southern Huanghai Sea, the sand ridge area in the eastern Huanghai islands and the Huanghai Troughs, the Jianggang sand ridge area in the western Huanghai Sea, the sand ridge area in the East China Sea shelf, and the sand ridge and sand wave area in the Taiwan Strait and Taiwan Banks. The distribution area of the sand ridges and sand waves covers more than 450,000 km2, wherein ~10,000 km2 in the Bohai Bay, ~200,000 km2 in the Huanghai Sea, ~200,000 km2 in the East China Sea shelf, and ~40,000 km2 in the Taiwan Strait and Taiwan Banks, respectively. The great mass of sand ridges are distributed within water depth of 5-160 m, with a total length of over 160 km and a main width of 5-10 km. The inner structure of the sand ridges presents features of high-angle inclined beddings, with main lithology of sands, sand-mud alternations partly visible, and a small number of mud cores. Dating results indicate that the sand ridges in the eastern part of the China Sea are mainly developed in the Holocene. Sea-level variation dominates the sand ridge evolution in the eastern part of the China Sea since the LGM, and the sand ridges developed in the area of < 60m water depth are appeared in bad activity, meanwhile sand ridges with good activity are still developed in large scale.

  18. Segmentation Control on Crustal Accretion: Insights From the Chile Ridge

    NASA Astrophysics Data System (ADS)

    Martinez, F.; Karsten, J. L.; Milman, M. S.; Klein, E. M.

    2002-12-01

    Controls on crustal accretion at mid-ocean ridges include spreading rate and mantle temperature and composition. Less studied is the effect of the segmentation geometry, although it has been known for some time that large offset transforms have significant effects on the extent of melting and lava compositions produced by ridges in their vicinity. The PANORAMA 4 expedition surveyed the Chile Ridge between 36°-43°S in order to examine the effects of ridge segmentation on crustal accretion. This section of the ridge is spreading uniformly at intermediate rates (~53 mm/yr) and rock sampling and regional data indicate a largely uniform mantle composition with no systematic changes in mantle thermal structure. Thus the segmentation geometry is the primary crustal accretion variable. The survey mapped and sampled 19 first order ridge segments and their transform offsets. The ridges range from 130 to 10 km in length with mapped transform offsets from 168 to 19 km. The segments primarily have axial valley morphology, with segments longer than ~65 km typically displaying central highs deepening toward segment ends. Mantle Bouguer anomalies (MBAs) show that these segments also have bulls eye lows associated with the central highs indicating thicker crust than at segment ends. Overall the mapped segments displays a trend of increasing depth and MBA, implying diminishing crustal production, with decreasing segment length and increasing transform offset. We examine the cause of this trend by modeling the mantle flow pattern generated by finite length ridge segments using the Phipps-Morgan and Forsyth (1988) algorithm. The results indicate that at a constant spreading rate mantle upwelling rates are greatest and extend deeper near the segment center, and that for segments that are significantly offset, upwelling rates decrease overall with decreasing segment length. The modeling implies that segmentation itself, even without cooling and lithospheric relief at transforms has a

  19. LakeMIP Kivu: Evaluating the representation of a large, deep tropical lake by a set of 1-dimensional lake models

    NASA Astrophysics Data System (ADS)

    Thiery, Wim; Stepanenko, Viktor; Darchambeau, François; Joehnk, Klaus; Martynov, Andrey; Mironov, Dmitrii; Perroud, Marjorie; van Lipzig, Nicole

    2013-04-01

    The African great lakes are of utmost importance for the local economy (fishing), as well as being essential to the survival of the local people. During the last decades, these lakes experienced fast changes in ecosystem structure and functioning and their future evolution is a major concern. In this study, for the first time a set of one-dimensional lake models are evaluated over East-Africa, in particular over Lake Kivu (2.28 °S; 28.98 °E). The unique limnology of meromictic Lake Kivu, with the importance of salinity and geothermal springs in a tropical high-altitude climate, presents a worthy challenge to the 1D-lake models currently involved in the Lake Model Intercomparison Project (LakeMIP). Furthermore, this experiment will serve as the basis for a future, more complex intercomparison, coupling lake models with atmospheric circulation models to analyse climate change effects on the lake. Meteorological observations from two automatic weather stations, one at Kamembe airport (Rwanda, 2003-2008), the other at ISP Bukavu (DRC, 2003-2011), are used to drive each of these models. For the evaluation, a unique dataset is used which contains over 150 temperature profiles recorded since 2002. The standard LakeMIP protocol is adapted to mirror the limnological conditions in Lake Kivu and to unify model parameters as far as possible. Since some lake models do not account for salinity and its effect upon lake stratification, two sets of simulations are performed with each model: one for the freshwater layer only (60 m) and one for the average lake depth (240 m) including salinity. Therewith, on the one hand it is investigated whether each model is able to reproduce the correct mixing regime in Lake Kivu and captures the controlling of this seasonality by the relative humidity, which constrains evaporation except during summer (JJA). On the other hand, the ability of different models to simulate salinity- and geothermal-induced effects upon deep water stratification is

  20. Planetary Lake Lander - A Robotic Sentinel to Monitor a Remote Lake

    NASA Technical Reports Server (NTRS)

    Pedersen, Liam; Smith, Trey; Lee, Susan; Cabrol, Nathalie; Rose, Kevin

    2012-01-01

    The Planetary Lake Lander Project is studying the impact of rapid deglaciation at a high altitude alpine lake in the Andes, where disrupted environmental, physical, chemical, and biological cycles result in newly emerging natural patterns. The solar powered Lake Lander robot is designed to monitor the lake system and characterize both baseline characteristics and impacts of disturbance events such as storms and landslides. Lake Lander must use an onboard adaptive science-on-the-fly approach to return relevant data about these events to mission control without exceeding limited energy and bandwidth resources. Lake Lander carries weather sensors, cameras and a sonde that is winched up and down the water column to monitor temperature, dissolved oxygen, turbidity and other water quality parameters. Data from Lake Lander is returned via satellite and distributed to an international team of scientists via web-based ground data systems. Here, we describe the Lake Lander Project scientific goals, hardware design, ground data systems, and preliminary data from 2011. The adaptive science-on-the-fly system will be described in future papers.

  1. Effects of Employing Ridge Regression in Structural Equation Models.

    ERIC Educational Resources Information Center

    McQuitty, Shaun

    1997-01-01

    LISREL 8 invokes a ridge option when maximum likelihood or generalized least squares are used to estimate a structural equation model with a nonpositive definite covariance or correlation matrix. Implications of the ridge option for model fit, parameter estimates, and standard errors are explored through two examples. (SLD)

  2. Patterns of organochlorine contamination in lake trout from Wisconsin waters of the Great Lakes

    USGS Publications Warehouse

    Miller, Michael A.; Madenjian, Charles P.; Masnado, Robert G.

    1992-01-01

    To investigate spatial and temporal patterns of organochlorine contamination in lake trout from Wisconsin waters of the Great Lakes, we examined laboratory contaminant analysis data of muscle tissue samples from Lake Michigan (n=317) and Lake Superior (n=53) fish. Concentrations of polychlorinated biphenyls (PCBs), chlordane, and dieldrin, reported as mg/kg wet weight in 620 mm to 640 mm mean length Lake Michigan lake trout, decreased over time. Mean total PCB concentration declined exponentially from 9.7 in 1975 to 1.9 in 1990. Total chlordane concentration declined 63 percent from 0.48 in 1983 to 0.18 in 1990, and dieldrin declined 52 percent during this same period, from 0.21 to 0.10. The bioaccumulation rate of PCBs is significantly lower for lake trout inhabiting Lake Michigan's midlake reef complex, compared to lake trout from the nearshore waters of western Lake Michigan. Organochlorine compound concentrations were greater in Lake Michigan lake trout than Lake Superior fish. Lake Superior lean lake trout and siscowet exhibited similar rates of PCB bioaccumulation despite major differneces in muscle tissue lipid content between the two subspecies. The lack of a significant difference in the PCB bioaccumulation rates of lean trout and siscowet suggests that lipid content may not be an important factor influencing PCB bioaccumulation in lake trout, within the range of lipid concentrations observed. Relative concentrations of the various organochlorine contaminants found in lake trout were highly correlated, suggesting similar mass balance processes for these compounds. Evidence presented revealing spatial and temporal patterns of organochlorine contamination may be of value in reestablishing self-sustaining populations of lake trout in Lake Michigan.

  3. Winter diet of lake herring (Coregonus artedi) in western Lake Superior

    USGS Publications Warehouse

    Link, Jason; Selgeby, James H.; Hoff, Michael H.; Haskell, Craig

    1995-01-01

    Lake herring (Coregonus artedi) and zooplankton samples were simultaneously collected through the ice in the Apostle Islands region of western Lake Superior to provide information on the winter feeding ecology of lake herring. Zooplankton constituted the entire diet of the 38 lake herring collected for this study. We found no evidence of piscivory, although it has been reported by anglers. Diet selectivities were calculated using a Wilcoxon signed-ranks test and showed a preference of lake herring for larger zooplankton, especially Diaptomus sicilis, whereas the smaller copepod,Cyclops bicuspidatus thomasi, and immature copepod stages were selected against. These data document that overwintering copepods are food for a broad size range of lake herring in winter.

  4. Mono Lake, California

    NASA Image and Video Library

    2017-03-24

    In eastern California, along the western edge of the Great Basin, sits Mono Lake. This is a salty remnant of a wetter era. Estimates are that the lake existed for at least 760,000 years. Now surrounded by mountain ranges, however, Mono Lake has no outlet; water entering the lake can only evaporate away, so Mono Lake is saltier than the ocean. South of the lake appear some of the geologic features known as Mono Craters. Geologists estimate that the Mono Craters last erupted about 650 years ago. The image was acquired July 7, 2016, covers an area of 22.6 by 34 km, and is located at 37.9 degrees north, 119 degrees west. http://photojournal.jpl.nasa.gov/catalog/PIA21518

  5. Synthetic Musk Fragrances in Lake Erie and Lake Ontario Sediment Cores

    PubMed Central

    Peck, Aaron M.; Linebaugh, Emily K.; Hornbuckle, Keri C.

    2009-01-01

    Two sediment cores collected from Lake Ontario and Lake Erie were sectioned, dated, and analyzed for five polycyclic musk fragrances and two nitro musk fragrances. The polycyclic musk fragrances were HHCB (Galaxolide), AHTN (Tonalide), ATII (Traseolide), ADBI (Celestolide), and AHMI (Phantolide). The nitro musk fragrances were musk ketone and musk xylene. Chemical analysis was performed by gas chromatography/mass spectrometry (GC/MS) and results from Lake Erie were confirmed using gas chromatography/triple-quadrupole mass spectrometry (GC/MS/MS). The chemical signals observed at the two sampling locations were different from each other due primarily to large differences in the sedimentation rates at the two sampling locations. HHCB was detected in the Lake Erie core while six compounds were detected in the Lake Ontario core. Using measured fragrance and 210Pb activity, the burden of synthetic musk fragrances estimated from these sediment cores is 1900 kg in Lake Erie and 18000 kg in Lake Ontario. The input of these compounds to the lakes is increasing. The HHCB accumulation rates in Lake Erie for 1979-2003 and 1990-2003 correspond to doubling times of 16 ± 4 yr and 8 ± 2 yr, respectively. The results reflect current U.S. production trends for the sum of all fragrance compounds. PMID:17007119

  6. Status of lake trout rehabilitation in the Northern Refuge of Lake Michigan

    USGS Publications Warehouse

    Madenjian, Charles P.; DeSorcie, Timothy J.

    1999-01-01

    The Northern Refuge in Lake Michigan was established in 1985 as part of a rehabilitation program to stock yearling lake trout Salvelinus namaycush in areas with the best potential for success. Stocking of hatchery-reared lake trout within the refuge began in 1986 at three reefs: Boulder Reef, Gull Island Reef, and Richards Reef. On each reef from 1991 to 1997 we conducted gill-net surveys during the fall spawning season to evaluate performance of adult lake trout, and we conducted beam trawl surveys for naturally reproduced age-0 lake trout in the spring. Criteria to evaluate performance included spawner density, growth, maturity, and mortality. We found no evidence of natural reproduction by lake trout from our surveys. Nevertheless, density of spawning lake trout on Boulder Reef (69 fish/305 m of gill net/night) and Gull Island Reef (34 fish/305 m of gill net/night) appeared to be sufficiently high to initiate a self-sustaining population. Growth and maturity rates of lake trout in the Northern Refuge were similar to those for lake trout stocked in the nearshore region of Lake Michigan. In the Northern Refuge, growth rate for the Marquette strain of lake trout was slightly higher than for the Lewis Lake strain. Annual mortality estimates from catch curve analyses ranged from 0.46 to 0.41, and therefore, these estimates approached a level that was considered to be sufficiently low to allow for a self-sustaining population. Thus, it appeared that the lack of evidence for natural reproduction by lake trout in the Northern Refuge should not be attributed to inability of the population to attain a sufficiently large stock of spawners.

  7. Water-Quality and Lake-Stage Data for Wisconsin Lakes, Water Year 2007

    USGS Publications Warehouse

    Wisconsin Water Science Center Lake-Studies Team: Rose, W. J.; Garn, H.S.; Goddard, G.L.; Marsh, S.B.; Olson, D.L.; Robertson, Dale M.

    2008-01-01

    The U.S. Geological Survey (USGS), in cooperation with local and other agencies, collects data at selected lakes throughout Wisconsin. These data, accumulated over many years, provide a data base for developing an improved understanding of the water quality of lakes. To make these data available to interested parties outside the USGS, the data are published annually in this report series. The locations of water-quality and lake-stage stations in Wisconsin for water year 2007 are shown in figure 1. A water year is the 12-month period from October 1 through September 30. It is designated by the calendar year in which it ends. Thus, the period October 1, 2005 through September 30, 2007 is called 'water year 2007.' The purpose of this report is to provide information about the chemical and physical characteristics of Wisconsin lakes. Data that have been collected at specific lakes, and information to aid in the interpretation of those data, are included in this report. Data collected include measurements of in-lake water quality and lake stage. Time series of Secchi depths, surface total phosphorus and chlorophyll a concentrations collected during non-frozen periods are included for all lakes. Graphs of vertical profiles of temperature, dissolved oxygen, pH, and specific conductance are included for sites where these parameters were measured. Descriptive information for each lake includes: location of the lake, area of the lake?s watershed, period for which data are available, revisions to previously published records, and pertinent remarks. Additional data, such as streamflow and water quality in tributary and outlet streams of some of the lakes, are published in another volume: 'Water Resources Data-Wisconsin, 2007.'

  8. Evaluation of Calendar Year 1997 Groundwater and Surface Water Quality Data For The Chestnut Ridge Hydrogeologic Regime At The U.S. Department of Energy Y-12 Plant, Oak Ridge, Tennessee

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Jones, S.B.

    1998-09-01

    This report presents an evaluation of the groundwater monitoring data obtained in the Chestnut Ridge Hydrogeologic Regime (Chestnut Ridge Regime) during calendar year (CY) 1997. The Chestnut Ridge Regime encompasses a section of Chestnut Ridge bordered by the U.S. Department of Energy (DOE) Y-12 Plant in Bear Creek Valley (BCV) to the north, Scarboro Road to the eas~ Bethel Valley Road to the south, and an unnamed drainage basin southwest of the Y-12 Plant (Figure 1). Groundwater quality monitoring is performed at hazardous and nonhazardous waste management facilities in the regime under the auspices of the Y-12 Plant Groundwater Protectionmore » Program (GWPP). The CY 1997 monitoring data are presented in Calendar Year 1997 Annual Groundwater Monitoring Report for the Chestnut Ridge Hydrogeolo~"c Regime at the US. Department of Energy Y-12 Plant, Oak Ridge, Tennessee (MA Technical Services, Inc. 1998), which also presents results of site-specific monitoring data evaluations required under the Resource Conservation and Recovery Act (RCIL4) post-closure permit (PCP) for the Chestnut Ridge Regime« less

  9. Circulation in the region of the Reykjanes Ridge in June-July 2015

    NASA Astrophysics Data System (ADS)

    Tillys, Petit; Herle, Mercier; Virginie, Thierry

    2017-04-01

    The Reykjanes Ridge is a major topographic feature of the North-Atlantic Ocean lying south of Iceland that strongly influences the pathways of the upper and lower limbs of the meridional overturning cell. The circulation in the vicinity of the Reykjanes Ridge is anticyclonic and characterized by a southwestward flow (the East Reykjanes Ridge Current, ERRC) along the eastern flank and a northeastward flow (the Irminger Current, IC) along the western flank. Even if it is admitted that the ERRC feeds the IC through a cross-ridge flow, details and magnitude of this circulation remain unclear. In this study, the circulation in the region of the Reykjanes Ridge was investigated based on ADCP and CTDO2 measurements carried out from the R/V Thalassa during the RREX cruise, which provided a snapshot of the water mass distribution and circulation during summer 2015. One hydrographic section followed the top of the Reykjanes Ridge between Iceland and 50˚ N and three other sections were carried out perpendicularly to the ridge at 62˚ N, 58.5˚ N and 56˚ N. Geostrophic transports were estimated by combining ADCP and hydrographic data. Those observations were used to provide an estimate of the circulation around the Ridge and to discuss the meridional evolutions of the ERRC and IC transports along the Ridge and their connection to the cross-Ridge flows. The section along the top of the Reykjanes Ridge allowed us to describe the cross ridge exchanges. A westward flow crossed the Ridge between Iceland and 53˚ N. Its top to bottom integrated transport was estimated at 17.7 Sv. Two main passages were identified for the westward crossing. A first passage is located near 57˚ N (Bight Fracture Zone, BFZ) in agreement with previous studies. More surprisingly, a second passage is located near 59˚ N. The top-to-bottom transports of those two main flows were estimated at 6.5 and 8 Sv respectively. The IC and ERRC top-to-bottom integrated transports were maximum at 58.5˚ N and

  10. Oxygen, hydrogen, sulfur, and carbon isotopes in the Pea Ridge magnetite-apatite deposit, southeast Missouri, and sulfur isotope comparisons to other iron deposits in the region

    USGS Publications Warehouse

    Johnson, Craig A.; Day, Warren C.; Rye, Robert O.

    2016-01-01

    Oxygen, hydrogen, sulfur, and carbon isotopes have been analyzed in the Pea Ridge magnetite-apatite deposit, the largest historic producer among the known iron deposits in the southeast Missouri portion of the 1.5 to 1.3 Ga eastern granite-rhyolite province. The data were collected to investigate the sources of ore fluids, conditions of ore formation, and provenance of sulfur, and to improve the general understanding of the copper, gold, and rare earth element potential of iron deposits regionally. The δ18O values of Pea Ridge magnetite are 1.9 to 4.0‰, consistent with a model in which some magnetite crystallized from a melt and other magnetite—perhaps the majority—precipitated from an aqueous fluid of magmatic origin. The δ18O values of quartz, apatite, actinolite, K-feldspar, sulfates, and calcite are significantly higher, enough so as to indicate growth or equilibration under cooler conditions than magnetite and/or in the presence of a fluid that was not entirely magmatic. A variety of observations, including stable isotope observations, implicate a second fluid that may ultimately have been meteoric in origin and may have been modified by isotopic exchange with rocks or by evaporation during storage in lakes.Sulfur isotope analyses of sulfides from Pea Ridge and seven other mineral deposits in the region reveal two distinct populations that average 3 and 13‰. Two sulfur sources are implied. One was probably igneous melts or rocks belonging to the mafic- to intermediate-composition volcanic suite that is present at or near most of the iron deposits; the other was either melts or volcanic rocks that had degassed very extensively, or else volcanic lakes that had trapped rising magmatic gases. The higher δ34S values correspond to deposits or prospects where copper is noteworthy—the Central Dome portion of the Boss deposit, the Bourbon deposit, and the Vilander prospective area. The correspondence suggests that (1) sulfur either limited the deposition

  11. Martian Wrinkle Ridge Topography: Evidence for Subsurface Faults from MOLA

    NASA Technical Reports Server (NTRS)

    Golombek, M. P.; Anderson, F. S.; Zuber, M. T.

    2000-01-01

    Mars Orbiter Laser Altimeter (MOLA) profiles across wrinkle ridges are characterized by plains surfaces at different elevations on either side that appear best explained by subsurface thrust faults that underlie the ridges and produce the offset.

  12. The geologic, geomorphic, and hydrologic context underlying options for long-term management of the Spirit Lake outlet near Mount St. Helens, Washington

    USGS Publications Warehouse

    Grant, Gordon E.; Major, Jon J.; Lewis, Sarah L.

    2017-01-01

    The 1980 eruption of Mount St. Helens produced a massive landslide and consequent pyroclastic currents, deposits of which blocked the outlet to Spirit Lake. Without an outlet, the lake began to rise, threatening a breaching of the blockage and release of a massive volume of water. To mitigate the hazard posed by the rising lake and provide an outlet, in 1984–1985 the U.S. Army Corps of Engineers bored a 2.6-km (8,500-ft) long tunnel through a bedrock ridge on the western edge of the lake. Locally, the tunnel crosses weak rock along faults, and external pressures in these weak zones have caused rock heave and support failures, which have necessitated periodic major repairs. During its more than 30-year lifetime, the tunnel has maintained the level of Spirit Lake at a safe elevation. The lake approaches its maximum safe operating level only when the tunnel closes for repair. The most recent major repair in early 2016 highlights the need for a reliable outlet that does not require repeated and expensive interventions and extended closures. The U.S. Forest Service, U.S. Army Corps of Engineers, and U.S. Geological Survey developed, reviewed, and analyzed an array of options for a long-term plan to remove the threat of catastrophic failure of the tunnel. In this report, we (1) provide background on natural hazards that can affect existing and alternative infrastructure; (2) evaluate the potential for tunnel failure and consequent breaching of the blockage posed by the current tunnel infrastructure; (3) evaluate potential consequences to downstream communities and infrastructure in the event of a catastrophic breaching of the blockage; (4) evaluate potential risks associated with alternative lake outlets; and (5) identify data and knowledge gaps that need to be addressed to fully evaluate options available to management.

  13. Paleolimnology of Lake Tanganyika, East Africa, over the past 100 k yr

    USGS Publications Warehouse

    Scholz, C.A.; King, J.W.; Ellis, G.S.; Swart, Peter K.; Stager, J.C.; Colman, Steven M.

    2003-01-01

    New sediment core data from a unique slow-sedimentation rate site in Lake Tanganyika contain a much longer and continuous record of limnological response to climate change than have been previously observed in equatorial regions of central Africa. The new core site was first located through an extensive seismic reflection survey over the Kavala Island Ridge (KIR), a sedimented basement high that separates the Kigoma and Kalemie Basins in Lake Tanganyika. Proxy analyses of paleoclimate response carried out on core T97-52V include paleomagnetic and index properties, TOC and isotopic analyses of organic carbon, and diatom and biogenic silica analyses. A robust age model based on 11 radiocarbon (AMS) dates indicates a linear, continuous sedimentation rate nearly an order of magnitude slower here compared to other core sites around the lake. This age model indicates continuous sedimentation over the past 79 k yr, and a basal age in excess of 100 k yr. The results of the proxy analyses for the past ??? 20 k yr are comparable to previous studies focused on that interval in Lake Tanganyika, and show that the lake was about 350 m lower than present at the Last Glacial Maximum (LGM). Repetitive peaks in TOC and corresponding drops in ??13C over the past 79 k yr indicate periods of high productivity and mixing above the T97-52V core site, probably due to cooler and perhaps windier conditions. From ??? 80 through ??? 58 k yr the ??13C values are relatively negative (-26 to -28???) suggesting predominance of algal contributions to bottom sediments at this site during this time. Following this interval there is a shift to higher values of ??13C, indicating a possible shift to C-4 pathway-dominated grassland-type vegetation in the catchment, and indicating cooler, dryer conditions from ??? 55 k yr through the LGM. Two seismic sequence boundaries are observed at shallow stratigraphic levels in the seismic reflection data, and the upper boundary correlates to a major discontinuity

  14. Patterns of egg deposition by lake trout and lake whitefish at Tawas artificial Reef, Lake Huron, 1990-1993

    USGS Publications Warehouse

    Foster, N.R.; Kennedy, G.W.; Munawar, M.; Edsall, T.; Leach, J.

    1995-01-01

    In August 1987, the Michigan Department of Natural Resources (MDNR), with the help and co-sponsorship of Walleyes for Iosco County, constructed Tawas artificial reef to improve recreational fishing in Tawas Bay. Post-construction assessment in October, 1987, by the MDNR found twice as many adult lake trout in a gill net set on the reef as in a similar net set off the reef, indicating that lake trout already had begun to investigate this new habitat. Similar netting efforts in October 1989 caught three times as many adults on the reef as off it, even though the on-reef net was set for less than one third as long a period. Using a remotely operated vehicle (ROV), we detected prespawning aggregations of lake trout on the reef in fall 1989, and MDNR biologists set emergent fly traps on the reef in April-May 1990-1991. These fry traps captured several newly emerged lake trout and lake whitefish fry, demonstrating that eggs of both species has hatched successfully. Gill netting in 1992-1993 by U.S. Fish and Wildlife Service biologists netted large numbers of ripe lake trout in late October and ripe lake whitefish in early to mid-November. The purpose of this paper is to describe the relative quantities of eggs deposited and the spatial patterns of egg deposition by lake trout and lake whitefish at Tawas artificial reef during 1990-1993.

  15. Lake Powell

    NASA Image and Video Library

    2007-09-20

    The white ring around Lake Powell tells the story. The surface is down 98 feet. This is critical, because Powell, Lake Mead, and other lakes along the Colorado River provide water for millions of people in five states. We are in the eighth year of a drought on the Colorado River. This year was the driest year ever reported in Southern California, and there is a severe drought in Northern California, down to less than 30-percent of snow pack. This ASTER image of part of Lake Powell was acquired in 2001. The gray area depicts the shrunken, reduced 2007 lake extent compared to the extended, larger black area in 2001. The image covers an area of 24 x 30 km, and is centered near 37.1 degrees north latitude, 111.3 degrees west longitude. This image from NASA Terra satellite. http://photojournal.jpl.nasa.gov/catalog/PIA10614

  16. National Lakes Assessment: A Collaborative Survey of the Nation's Lakes

    EPA Science Inventory

    The National Lakes Assessment A Collaborative Survey of the Nation's Lakes presents the results of an unprecedented assessment of the nation’s lakes. This report is part of the National Aquatic Resource Surveys, a series of statistically based surveys designed to provide the pub...

  17. Testing models for the formation of the equatorial ridge on Iapetus via crater counting

    NASA Astrophysics Data System (ADS)

    Damptz, Amanda L.; Dombard, Andrew J.; Kirchoff, Michelle R.

    2018-03-01

    Iapetus's equatorial ridge, visible in global views of the moon, is unique in the Solar System. The formation of this feature is likely attributed to a key event in the evolution of Iapetus, and various models have been proposed as the source of the ridge. By surveying imagery from the Cassini and Voyager missions, this study aims to compile a database of the impact crater population on and around Iapetus's equatorial ridge, assess the relative age of the ridge from differences in cratering between on ridge and off ridge, and test the various models of ridge formation. This work presents a database that contains 7748 craters ranging from 0.83 km to 591 km in diameter. The database includes the study area in which the crater is located, the latitude and longitude of the crater, the major and minor axis lengths, and the azimuthal angle of orientation of the major axis. Analysis of crater orientation over the entire study area reveals that there is no preference for long-axis orientation, particularly in the area with the highest resolution. Comparison of the crater size-frequency distributions show that the crater distribution on the ridge appears to be depleted in craters larger than 16 km with an abruptly enhanced crater population less than 16 km in diameter up to saturation. One possible interpretation is that the ridge is a relatively younger surface with an enhanced small impactor population. Finally, the compiled results are used to examine each ridge formation hypothesis. Based on these results, a model of ridge formation via a tidally disrupted sub-satellite appears most consistent with our interpretation of a younger ridge with an enhanced small impactor population.

  18. Climatological assessment of spatiotemporal trends in observational monthly snowfall totals and extremes over the Canadian Great Lakes Basin

    NASA Astrophysics Data System (ADS)

    Baijnath, Janine; Duguay, Claude; Sushama, Laxmi; Huziy, Oleksandr

    2017-04-01

    The Laurentian Great Lakes Basin (GLB) is susceptible to snowfall events that derive from extratropical cyclones and heavy lake effect snowfall (HLES). The former is generated by quasigeostropic forcing from positive temperature or vorticity advection associated with low-pressure centres. HLES is produced by planetary boundary layer (PBL) convection that is initiated as a result of cold and dry continental air mass advecting over relatively warm lakes and generating turbulent moisture and heat fluxes into the PBL. HLES events can have disastrous impacts on local communities such as the November 2014 Buffalo storm that caused 13 fatalities. Albeit the many HLES studies, most are focused on specific case study events with a discernible under examination of climatological HLES trend analyses for the Canadian GLB. The research objectives are to first determine the historical, climatological trends in monthly snowfall totals and to examine potential surface and atmospheric variables driving the resultant changes in HLES. The second aims to analyze the historical extremes in snowfall by assessing the intensity, frequency, and duration of snowfall within the domain of interest. Spatiotemporal snowfall and precipitation trends are computed for the 1982 to 2015 period using Daymet (Version 3) monthly gridded observational datasets from the Oak Ridge National Laboratory. The North American Regional Reanalysis (NARR), NOAA Optimum Interpolation Sea Surface Temperature (OISST), and the Canadian Ice Service (CIS) datasets are also used for evaluating trends in HLES driving variables such as air temperature, lake surface temperature (LST), ice cover concentration, omega, and vertical temperature gradient (VTGlst-850). Climatological trends in monthly snowfall totals show a significant decrease along the Ontario snowbelt of Lake Superior, Lake Huron and Georgian Bay at the 90 percent confidence level. These results are attributed to significant warming in LST, significant

  19. High Resolution Seismic Imaging of the Trench Canyon Fault Zone, Mono Lake, Northeastern California

    NASA Astrophysics Data System (ADS)

    Novick, M. W.; Jayko, A. S.; Roeske, S.; McClain, J. S.; Hart, P. E.; Boyle, M.

    2009-12-01

    High resolution seismic imaging of Mono Lake, located in northeastern California, has revealed an approximately northwest striking fault in the area to the west of aerially exposed Negit Volcano. This fault, henceforth referred to as the Trench Canyon Fault (TCF), has also been mapped onshore along a correlating strike as far north as Cedar Hill Volcano, located to the northeast of the lake on the California/Nevada border. Onshore, the TCF was mapped for approximately 10 kilometers using air photos, DEM images, and standard geologic pace and compass mapping techniques. The TCF post- dates the last glacial maximum, evidenced by the cutting of wave cut benches along Cedar Hill Volcano. Relict, non-historic shorelines, left by the steady evaporation of Mono Lake beginning approximately 13k, are also repeatedly cut by the fault. Additional evidence of fault presence includes sag ponds, pressure ridges, tectonically fractured rocks, and normal fault scarps found along strike. Offshore, DEM images show a northeast striking structure to the northwest of Negit Volcano, which is co-linear with the onshore TCF. High resolution seismic imaging of the structure, using an applied acoustic/SIG mini-sparker system, reveals steeply dipping Holocene sediments, as well as volcanic deposits from active vents which have erupted in the last 1000 years, offset by the fault. Detailed structural analysis of the previously unstudied Trench Canyon Fault (TFC) and faults in the Cedar Hill region of northern California, along with seismic studies of sediments beneath Mono Lake not only allow for a better comprehension of this minor fault system, but provide greater understanding of the larger and more complex Walker Lane Shear Zone. Fault analyses, combined and correlated with those from CHV, give a better understanding of how slip is transferred into the complicated Mina defection to the east, from the dextral and normal faults along the Sierra Nevada Range front.

  20. Hydrology of the Lake Deaton and Lake Okahumpka area, Northeast Sumter County, Florida

    USGS Publications Warehouse

    Simonds, Edward P.; German, E.R.

    1980-01-01

    The Floridan aquifer in the Lake Deaton and Lake Okahumpka area is 50 to 130 feet below land surface. During the 16-year period 1963-78 lake evaporation exceeded rainfall by 0.4 inches. Drainage from Lake Deaton and its surrounding area goes into Chitty Chatty Creek and on the Hogeye Sink when the altitude of the potentiometric surface of the Floridan aquifer is low. During a higher altitude of the Floridan potentiometric surface, Hogeye Sink may discharge water; this water, along with the normal runoff, goes into Lake Okahumpka. Average lake fluctuation is 1.5 to 2.0 feet per year. Lake Deaton supports a large population of blue-green algae and Lake Okahumpka is choked with aquatic plants. The water quality of the two lakes differ, with Lake Deaton having a sodium chloride water and Lake Okahumpka having a calcium bicarbonate water. Analysis of water and bottom material samples showed that only cadmium and mercury exceeded the Florida Department of Environmental Regulation 's criteria for Class III waters; however, the amounts detected were at or slightly above the limits of the analytical method. (USGS)

  1. Coral-gravel storm ridges: examples from the tropical Pacific and Caribbean

    USGS Publications Warehouse

    Richmond, Bruce M.; Morton, Robert A.

    2007-01-01

    Extreme storms in reef environments have long been recognized as a mechanism for depositing ridges of reef-derived coarse clastic sediment. This study revisits the storm ridges formed by Tropical Cyclone Bebe on Funafuti, Tuvalu and Tropical Cyclone Ofa on Upolu, Western Samoa in the South Pacific, and Hurricane Lenny on Bonaire, Netherlands Antilles in the Caribbean. Ridge characteristics produced by these storms include: heights of 1–4 m, widths of 8–50 m, and lengths up to 18 km. The ridges tend to be higher and steeper on their landward margins than on their seaward margins and are composed mostly of re-worked coral rubble derived from reef front settings with smaller amounts of fresh broken coral (5–30%). Characteristics of these modern gravel storm ridges can be used to help identify ancient storm deposits and to differentiate between other coarse-grained deposits such as those created by tsunamis.

  2. The crustal structure of the Cocos ridge off Costa Rica

    NASA Astrophysics Data System (ADS)

    Walther, Christian H. E.

    2003-03-01

    The submarine Cocos ridge in the northwestern Panamá basin, a bathymetric feature more than 1000-km long and 250-500 km broad, is about 2 km shallower than the adjacent basin. It is generally interpreted as the trace of the Galápagos hot spot. Two 127- and 260-km long seismic wide-angle sections were recorded along and across this ridge, offshore the Osa peninsula, Costa Rica. Crustal thickening is seen everywhere along the sections. On the northwestern outer ridge flank, increased thickness is exclusively attributed to the upper crust and expressed by 2-km thick flow basalts. The Quepos plateau caps the upper crust in this area. Toward the center of the Cocos ridge, the Moho deepens from 11-12 to 21 km depth and crustal thickening is almost entirely attributed to the lower crust which makes up 80% of the crust and is three times the thickness of normal oceanic lower crust. It is homogeneously structured and the velocities which range from 6.5 km/s at the top to 7.35 km/s at the base are comparable to normal lower crust under these depth conditions and suggest no differences to a gabbroic rock composition. Similarities to the crustal velocity structure of Iceland, central Kerguelen plateau, and Broken ridge are consistent with a formation of this 13-15 Ma old Cocos ridge segment by excessive magmatism in a near-plate boundary setting.

  3. Using submarine lava pillars to record mid-ocean ridge eruption dynamics

    USGS Publications Warehouse

    Gregg, Tracy K.P.; Fornari, Daniel J.; Perfit, Michael R.; Ridley, W. Ian; Kurz, Mark D.

    2000-01-01

    Submarine lava pillars are hollow, glass-lined, basaltic cylinders that occur at the axis of the mid-ocean ridge, and within the summit calderas of some seamounts. Typically, pillars are ~1-20 m tall and 0.25-2.0 m in diameter, with subhorizontal to horizontal glassy selvages on their exterior walls. Lava pillars form gradually during a single eruption, and are composed of lava emplaced at the eruption onset as well as the last lava remaining after the lava pond has drained. On the deep sea floor, the surface of a basaltic lava flow quenches to glass within 1 s, thereby preserving information about eruption dynamics, as well as chemical and physical properties of lava within a single eruption. Investigation of different lava pillars collected from a single eruption allows us to distinguish surficial lava-pond or lava-lake geochemical processes from those operating in the magma chamber. Morphologic, major-element, petrographic and helium analyses were performed on portions of three lava pillars formed during the April 1991 eruption near 9°50'N at the axis of the East Pacific Rise. Modeling results indicate that the collected portions of pillars formed in ~2-5 h, suggesting a total eruption duration of ~8-20 h. These values are consistent with observed homogeneity in the glass helium concentrations and helium diffusion rates. Major-element compositions of most pillar glasses are homogeneous and identical to the 1991 flow, but slight chemical variations measured in the outermost portions of some pillars may reflect post-eruptive processes rather than those occurring in subaxial magma bodies. Because lava pillars are common at mid-ocean ridges (MORs), the concepts and techniques we present here may have important application to the study of MOR eruptions, thereby providing a basis for quantitative comparisons of volcanic eruptions in geographically and tectonically diverse settings. More research is needed to thoroughly test the hypotheses presented here. (C) 2000

  4. Water-Quality and Lake-Stage Data for Wisconsin Lakes, Water Year 2006

    USGS Publications Warehouse

    Rose, W.J.; Garn, H.S.; Goddard, G.L.; Marsh, S.B.; Olson, D.L.; Robertson, Dale M.

    2007-01-01

    The U.S. Geological Survey (USGS), in cooperation with local and other agencies, collects data at selected lakes throughout Wisconsin. These data, accumulated over many years, provide a data base for developing an improved understanding of the water quality of lakes. To make these data available to interested parties outside the USGS, the data are published annually in this report series. The locations of water-quality and lake-stage stations in Wisconsin for water year 2006 are shown in figure 1. A water year is the 12-month period from October 1 through September 30. It is designated by the calendar year in which it ends. Thus, the period October 1, 2005 through September 30, 2006 is called 'water year 2006.' The purpose of this report is to provide information about the chemical and physical characteristics of Wisconsin lakes. Data that have been collected at specific lakes, and information to aid in the interpretation of those data, are included in this report. Data collected include measurements of in-lake water quality and lake stage. Time series of Secchi depths, surface total phosphorus and chlorophyll a concentrations collected during non-frozen periods are included for all lakes. Graphs of vertical profiles of temperature, dissolved oxygen, pH, and specific conductance are included for sites where these parameters were measured. Descriptive information for each lake includes: location of the lake, area of the lake's watershed, period for which data are available, revisions to previously published records, and pertinent remarks. Additional data, such as streamflow and water quality in tributary and outlet streams of some of the lakes, are published in another volume: 'Water Resources Data-Wisconsin, 2006.' Water-resources data, including stage and discharge data at most streamflow-gaging stations, are available through the World Wide Web on the Internet. The Wisconsin Water Science Center's home page is at http://wi.water.usgs.gov/. Information on the

  5. Diet and prey selection by Lake Superior lake trout during springs 1986-2001

    USGS Publications Warehouse

    Ray, B.A.; Hrabik, T.R.; Ebener, M.P.; Gorman, O.T.; Schreiner, D.R.; Schram, S.T.; Sitar, S.P.; Mattes, W.P.; Bronte, C.R.

    2007-01-01

    We describe the diet and prey selectivity of lean (Salvelinus namaycush namaycush) and siscowet lake trout (S. n. siscowet) collected during spring (April–June) from Lake Superior during 1986–2001. We estimated prey selectivity by comparing prey numerical abundance estimates from spring bottom trawl surveys and lake trout diet information in similar areas from spring gill net surveys conducted annually in Lake Superior. Rainbow smelt (Osmerus mordax) was the most common prey and was positively selected by both lean and siscowet lake trout throughout the study. Selection by lean lake trout for coregonine (Coregonus spp.) prey increased after 1991 and corresponded with a slight decrease in selection for rainbow smelt. Siscowet positively selected for rainbow smelt after 1998, a change that was coincident with the decrease in selection for this prey item by lean lake trout. However, diet overlap between lean and siscowet lake trout was not strong and did not change significantly over the study period. Rainbow smelt remains an important prey species for lake trout in Lake Superior despite declines in abundance.

  6. Biology, population structure, and estimated forage requirements of lake trout in Lake Michigan

    USGS Publications Warehouse

    Eck, Gary W.; Wells, LaRue

    1983-01-01

    Data collected during successive years (1971-79) of sampling lake trout (Salvelinus namaycush) in Lake Michigan were used to develop statistics on lake trout growth, maturity, and mortality, and to quantify seasonal lake trout food and food availability. These statistics were then combined with data on lake trout year-class strengths and age-specific food conversion efficiencies to compute production and forage fish consumption by lake trout in Lake Michigan during the 1979 growing season (i.e., 15 May-1 December). An estimated standing stock of 1,486 metric tons (t) at the beginning of the growing season produced an estimated 1,129 t of fish flesh during the period. The lake trout consumed an estimated 3,037 t of forage fish, to which alewives (Alosa pseudoharengus) contributed about 71%, rainbow smelt (Osmerus mordax) 18%, and slimy sculpins (Cottus cognatus) 11%. Seasonal changes in bathymetric distributions of lake trout with respect to those of forage fish of a suitable size for prey were major determinants of the size and species compositions of fish in the seasonal diet of lake trout.

  7. Lakes and lake-like waters of the Hawaiian Archipelago

    USGS Publications Warehouse

    Maciolek, J.A.

    1982-01-01

    This summary of Hawaiian lacustrine limnology is based on 12 years of field and literature surveys of archipelagic inland waters. Lakes here are distinguished from other standing waters by limits on surface oceanic area (> 0.1 ha) and depth (> 2 m), and by the absence of flatural surface oceanic connection. A variety of extinct and existing water bodies, sometimes referred to as lakes, are noted. Six lakes are described. Five of them are in crater basins, 3 are freshwater, and 2 are elevated (highest = 3969 m). The scarcity of elevated lakes results from general permeability of the substrata. Among the 6 lakes, surface areas range from 0.22 to 88 ha and maximum depths from 3 to 248 m. Naturally occurring aquatic biota generally is low in species diversity except for phytoplankton; fishes and submersed vascular plants are absent. Two lowland lakes, freshwater Green (Wai a Pele) and saline Kauhak6, are described for the first time. Profundal Kauhak6, 248 m deep, has a surface area of only 0.35 ha, which results in an extraordinary relative depth of 370%. It is permanently stratified, a condition apparently due primarily to the unique morphometry of its basin. 

  8. Seismic imaging of the Formosa Ridge cold seep site offshore of southwestern Taiwan

    NASA Astrophysics Data System (ADS)

    Hsu, Ho-Han; Liu, Char-Shine; Morita, Sumito; Tu, Shu-Lin; Lin, Saulwood; Machiyama, Hideaki; Azuma, Wataru; Ku, Chia-Yen; Chen, Song-Chuen

    2017-12-01

    Multi-scale reflection seismic data, from deep-penetration to high-resolution, have been analyzed and integrated with near-surface geophysical and geochemical data to investigate the structures and gas hydrate system of the Formosa Ridge offshore of southwestern Taiwan. In 2007, dense and large chemosynthetic communities were discovered on top of the Formosa Ridge at water depth of 1125 m by the ROV Hyper-Dolphin. A continuous and strong BSR has been observed on seismic profiles from 300 to 500 ms two-way-travel-time below the seafloor of this ridge. Sedimentary strata of the Formosa Ridge are generally flat lying which suggests that this ridge was formed by submarine erosion processes of down-slope canyon development. In addition, some sediment waves and mass wasting features are present on the ridge. Beneath the cold seep site, a vertical blanking zone, or seismic chimney, is clearly observed on seismic profiles, and it is interpreted to be a fluid conduit. A thick low velocity zone beneath BSR suggests the presence of a gas reservoir there. This "gas reservoir" is shallower than the surrounding canyon floors along the ridge; therefore as warm methane-rich fluids inside the ridge migrate upward, sulfate carried by cold sea water can flow into the fluid system from both flanks of the ridge. This process may drive a fluid circulation system and the active cold seep site which emits both hydrogen sulfide and methane to feed the chemosynthetic communities.

  9. Seismic and Tectonic Monitoring of the Endeavour Ridge Segment—Recent and Future Expansion of Ocean Networks Canada's NEPTUNE Observatory on the Juan de Fuca Ridge

    NASA Astrophysics Data System (ADS)

    Heesemann, M.; Davis, E. E.; Scherwath, M.; Kao, H.; Coogan, L. A.; Rogers, G. C.; Wilcock, W. S. D.

    2016-12-01

    Ocean Networks Canada's (ONC) NEPTUNE observatory provides real-time access to sensors on the Endeavour Ridge Segment (Endeavour)—a focus site on the Juan de Fuca Ridge System that is complementary to one on Axial Volcano that is connected through the Ocean Observatories Initiative's (OOI) Cabled Array. While first instruments (including cameras, a short-period seismometer, and vent monitoring instruments) installed at the Main Endeavour vent field have been sending data since summer 2010, unreliable extension cables precluded continuous time-series from other nearby locations. With the successful installation of four extension cables, the summer of 2016 represents an important milestone in the instrumentation of the Endeavour Ridge Segment. We will present an overview of the data that are available in near real-time from Endeavour and new instrumentation that is scheduled for installation in 2017, and highlight first results derived from the new seismo-tectonic network now in operation. This network consists of three short-period seismometers (Mothra Field, Main Endeavour Field, Regional Circulation North), one broadband seismometer (western Ridge Flank), and four bottom pressure recorders (Mothra Field, Regional Circulation South, Main Endeavour Field, western Ridge Flank). The pressure recorders will provide both seismic and oceanographic data, and allow to measure differential vertical motion among the sites. We will also highlight a new technique to determine long period seafloor deformation from broadband seismometer mass-position measurements, using data from the Ridge Flank instrument as an example.

  10. Ridging and strength in modeling the thickness distribution of Arctic sea ice

    NASA Astrophysics Data System (ADS)

    Flato, Gregory M.; Hibler, William D.

    1995-09-01

    A theory describing evolution of the ice thickness distribution (the probability density of ice thickness) was proposed by Thorndike et al. (1975) and has been used in several sea ice models. The advantage of this theory over the widely used two-level formulation is that it treats ridging explicitly as a redistribution of ice thickness, and ice strength as a function of energy losses incurred by ridge formation. However, the parameterization of these processes remains rather speculative and largely untested, and so our purpose here is to explore these parameterizations using a numerical model based on this theory. The model uses a 160-km resolution grid of the Arctic and 7 years of observed atmospheric forcing data (1979-1985). Monthly oceanic heat flux and current fields are obtained from a 40-km resolution coupled ice-ocean model run separately with the same forcing. By requiring the computed monthly mean ice drift to have the same magnitude as observed buoy drift, we estimate the primary strength parameter: the ratio of total to potential energy change during ridging. This ratio depends on the value of other parameters; however, the standard case has a ratio of 17 which is within the range estimated by Hopkins (1994) in simulations of individual ridging events. The effects of ridge redistribution and shear ridging parameters are illustrated by a series of sensitivity studies and comparisons between observed and modeled ice thickness distributions and ridge statistics. In addition, these comparisons highlight the following shortcomings of the thickness distribution theory as it is presently implemented: first, the process of first-year to multiyear ridge consolidation is ignored; and second, the observed preferential melt of thick ridged ice is not reproduced.

  11. Lake Powell

    NASA Technical Reports Server (NTRS)

    2007-01-01

    The white ring around Lake Powell tells the story. The surface is down 98 feet. This is critical, because Powell, Lake Mead, and other lakes along the Colorado River provide water for millions of people in five states. We are in the eighth year of a drought on the Colorado River. This year was the driest year ever reported in Southern California, and there is a severe drought in Northern California, down to less than 30-percent of snow pack. This ASTER image of part of Lake Powell was acquired in 2001. The gray area depicts the shrunken, reduced 2007 lake extent compared to the extended, larger black area in 2001.

    The image covers an area of 24 x 30 km, and is centered near 37.1 degrees north latitude, 111.3 degrees west longitude.

    The U.S. science team is located at NASA's Jet Propulsion Laboratory, Pasadena, Calif. The Terra mission is part of NASA's Science Mission Directorate.

  12. Micro-imager View: Layers in 'Vera Rubin Ridge,' Mars

    NASA Image and Video Library

    2017-09-13

    This view of "Vera Rubin Ridge" from the Chemistry and Camera (ChemCam) instrument on NASA's Curiosity Mars rover shows multiple sedimentary layers and fracture-filling deposits of minerals. Buried layers of what is now a ridge became fractured, and the fractures were filled with mineral deposits precipitated from underground fluids that moved through the fractures. ChemCam's telescopic Remote Micro-Imager took the 10 component images of this mosaic on July 3, 2017, during the 1,745th Martian day, or sol, of Curiosity's work on Mars. The camera was about 377 feet (115 meters) away from the pictured portion of the ridge. The rover's location at the time, shown in a Sol 1741 traverse map, was west of the place where it began its ascent up the ridge about two months later. The scale bar at lower right indicates how wide a feature 9 inches (22.8 centimeters) in width would look in the middle portion of the scene. https://photojournal.jpl.nasa.gov/catalog/PIA21852

  13. Ciscoes (Coregonus, subgenus Leucichthys) of the Laurentian Great Lakes and Lake Nipigon

    USGS Publications Warehouse

    Eshenroder, Randy L.; Vecsei, Paul; Gorman, Owen T.; Yule, Daniel; Pratt, Thomas C.; Mandrak, Nicholas E.; Bunnell, David B.; Muir, Andrew M.

    2016-01-01

    This study of the ciscoes (Coregonus, subgenus Leucichthys) of the Great Lakes and Lake Nipigon represents a furtherance through 2015 of field research initiated by Walter Koelz in 1917 and continued by Stanford Smith in the mid-1900s—a period spanning nearly a century. Like Koelz’s study, this work contains information on taxonomy, geographical distribution, ecology, and status of species (here considered forms). Of the seven currently recognized forms (C. artedi, C. hoyi, C. johannae, C. kiyi, C. nigripinnis, C. reighardi, and C. zenithicus) described by Koelz as major in his 1929 monograph, two (C. johannae and C. reighardi) are extinct. In addition, C. alpenae, described by Koelz but subsequently synonymized with C. zenithicus, although extinct, is recognized as valid making a total of eight major forms. Six of these forms, all but C. artedi and C. hoyi, have been lost from Lake Michigan, and seven have been lost from Lake Huron, leaving in Lake Huron only C. artedi and an introgressed deepwater form that we term a hybrid swarm. C. artedi appears, like its sister form C. alpenae, to have been lost from Lake Erie. Only C. artedi remains extant in Lake Ontario, its three sister forms (C. hoyi, C. kiyi, and C. reighardi) having disappeared long ago.Lakes Superior and Nipigon have retained their original species flocks consisting of four forms each: C. artedi, C. hoyi, and C. zenithicus in both lakes; C. kiyi in Lake Superior; and C. nigripinnis in Lake Nipigon. Morphological deviations from the morphotypes described by Koelz have been modest in contemporary samples. Overall, C. kiyi and C. artedi were the most morphologically stable forms while C. hoyi, C. nigripinnis, and C. zenithicus were the least stable. Although contemporary populations of C. artedi from Lakes Michigan and Huron are highly diverged from the morphotypes described by Koelz, the contemporary samples were of undescribed deep-bodied forms unlikely to have been sampled by Koelz because of

  14. Sedimentary constraints on late Quaternary lake-level fluctuations at Bear Lake, Utah and Idaho

    USGS Publications Warehouse

    Smoot, J.P.; Rosenbaum, J.G.

    2009-01-01

    A variety of sedimentological evidence was used to construct the lake-level history for Bear Lake, Utah and Idaho, for the past ???25,000 years. Shorelines provide evidence of precise lake levels, but they are infrequently preserved and are poorly dated. For cored sediment similar to that in the modern lake, grain-size distributions provide estimates of past lake depths. Sedimentary textures provide a highly sensitive, continuous record of lake-level changes, but the modern distribution of fabrics is poorly constrained, and many ancient features have no modern analog. Combining the three types of data yields a more robust lake-level history than can be obtained from any one type alone. When smooth age-depth models are used, lake-level curves from multiple cores contain inconsistent intervals (i.e., one record indicates a rising lake level while another record indicates a falling lake level). These discrepancies were removed and the multiple records were combined into a single lake-level curve by developing age-depth relations that contain changes in deposition rate (i.e., gaps) where indicated by sedimentological evidence. The resultant curve shows that, prior to 18 ka, lake level was stable near the modern level, probably because the lake was overflowing. Between ca. 17.5 and 15.5 ka, lake level was ???40 m below the modern level, then fluctuated rapidly throughout the post-glacial interval. Following a brief rise centered ca. 15 ka ( = Raspberry Square phase), lake level lowered again to 15-20 m below modern from ca. 14.8-11.8 ka. This regression culminated in a lowstand to 40 m below modern ca. 12.5 ka, before a rapid rise to levels above modern ca. 11.5 ka. Lake level was typically lower than present throughout the Holocene, with pronounced lowstands 15-20 m below the modern level ca. 10-9, 7.0, 6.5-4.5, 3.5, 3.0-2.5, 2.0, and 1.5 ka. High lake levels near or above the modern lake occurred ca. 8.5-8.0, 7.0-6.5, 4.5-3.5, 2.5, and 0.7 ka. This lake-level history

  15. Fat content of the flesh of siscowets and lake trout from Lake Superior

    USGS Publications Warehouse

    Eschmeyer, Paul H.; Phillips, Arthur M.

    1965-01-01

    Samples of flesh were excised from the middorsal region of 67 siscowets (Salvelinus namaycush siscowet) and 46 lake trout (Salvelinus n. namaycush) collected from Lake Superior. Chemical analysis of the samples revealed a range in fat content (dry weight) of 32.5 to 88.8 per cent in siscowets and 6.6 to 52.3 per cent in lake trout. Percentage fat increased progressively with increase in length of fish in both forms, but the average rate of increase was far greater for siscowets than for lake trout at lengths between 12 and 20 inches. Despite substantial individual variation, the percentage fat in the two forms was widely different and without overlap at all comparable lengths. The range in iodine number of the fat was 100 to 160 for siscowets and 103 to 161 for lake trout; average values were generally lower for siscowets than for lake trout among fish of comparable length. Percentage fat and relative weight were not correlated significantly in either subspecies. The fat content of flesh samples from a distinctive subpopulation of Lake Superior lake trout known as 'humpers' was more closely similar to that of typical lean lake trout than to siscowets, but the rate of increase in fat with increasing length was greater than for lean lake trout. Flesh samples from hatchery-reared stocks of lake trout, hybrid lake trout X siscowets, and siscowets tended to support the view that the wide difference in fat content between siscowets and lake trout is genetically determined.

  16. Ridges and Flows

    NASA Image and Video Library

    2015-11-16

    Located southwest of Olympus Mons, this image captured by NASA 2001 Mars Odyssey spacecraft shows part of a complex region that has undergone several geologic processes. The hills have been modified by wind, creating narrow ridges, and then the entire region has been covered with volcanic flows from Olympus Mons. Orbit Number: 60744 Latitude: 13.4267 Longitude: 220.554 Instrument: VIS Captured: 2015-08-24 10:00 http://photojournal.jpl.nasa.gov/catalog/PIA20093

  17. Building of tropical beach ridges, northeastern Queensland, Australia: Cyclone inundation and aeolian decoration

    NASA Astrophysics Data System (ADS)

    Tamura, Toru; Nicholas, William; Brooke, Brendan; Oliver, Thomas

    2016-04-01

    Processes associated with tropical cyclones are thought responsible for building coarse sand beach ridges along the northeastern Queensland coast, Australia. While these ridges are expected to be geological records of the past cyclone, they question the general consensus of the aeolian genesis of sandy beach ridges. To explore the ridge-forming process, we carried out the GPR survey, auger drilling, pit excavation, grain-size analysis, and OSL dating for coarse sand beach ridges at the Cowley Beach, northeastern Queensland. The Cowley Beach is a mesotidal beach characterized by a low-tide terrace and steep beach face. Ten beach ridges are recognized along the survey transect that extends 700 m inland from the shore. 37 OSL ages are younger seawards, indicating the seaward accretion of the ridge sequence over the last 2700 years. The highest ridge is +5.1 m high above AHD (Australian Height Datum). Two GPR units are bounded by a groundwater surface at c. +1.5 m AHD. The upper unit is characterized by horizontal to hummocky reflectors punctuated by seaward dipping truncation surfaces. These reflectors in places form dome-like structure that appears to be the nucleus of a beach ridge. The shape and level (+2.5 m AHD) of the dome are similar to those of the present swash berm. The lower unit shows a sequence of reflectors that dip at an angle of present beach face. The sequence is dissected by truncation surfaces, some of which are continuous to those in the upper unit. Coarse sand mainly forms beach ridge deposits below +4.0 m AHD, while a few higher ridges have an upward fining layer composed of medium sand above +4.0 m, which is finer than aeolian ripples found on the backshore during the survey. In addition, pumice gravel horizons underlie the examined ridge crests. The sequence of seaward dipping reflectors indicates that the Cowley Beach, like other many sandy beaches, has prograded during onshore sand accretion by fairweather waves and has been eroded by storms

  18. Holifield Heavy-Ion Research Facility at Oak Ridge

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Jones, C.M.

    1977-01-01

    A new heavy-ion accelerator facility is now under construction at the Oak Ridge National Laboratory. A brief description of the scope and schedule of this project is given, and the new large tandem accelerator, which will be a major element of the facility is discussed in some detail. Several studies which have been made or are in progress in Oak Ridge in preparation for operation of the tandem accelerator are briefly described.

  19. Mid Ocean Ridge Processes at Very Low Melt Supply : Submersible Exploration of Smooth Ultramafic Seafloor at the Southwest Indian Ridge, 64 degree E

    NASA Astrophysics Data System (ADS)

    Cannat, M.; Agrinier, P.; Bickert, M.; Brunelli, D.; Hamelin, C.; Lecoeuvre, A.; Lie Onstad, S.; Maia, M.; Prampolini, M.; Rouméjon, S.; Vitale Brovarone, A.; Besançon, S.; Assaoui, E. M.

    2017-12-01

    Mid-ocean ridges are the Earth's most extensive and active volcanic chains. They are also, particularly at slow spreading rates, rift zones, where plate divergence is in part accommodated by faults. Large offset normal faults, also called detachments, are characteristic of slow-spreading ridges, where they account for the widespread emplacement of mantle-derived rocks at the seafloor. In most cases, these detachments occur together with ridge magmatism, with melt injection and faulting interacting to shape the newly formed oceanic lithosphere. Here, we seek to better understand these interactions and their effects on oceanic accretion by studying the end-member case of a ridge where magmatism is locally almost absent. The portion of the Southwest Indian ridge we are studying has an overal low melt supply, focused to discrete axial volcanoes, leaving almost zero melt to intervening sections of the axial valley. One of these nearly amagmatic section of the ridge, located at 64°E, has been the focus of several past cruises (sampling, mapping and seismic experiments). Here we report on the most recent cruise to the area (RV Pourquoi Pas? with ROV Victor; dec-jan 2017), during which we performed high resolution mapping, submersible exploration and sampling of the ultramafic seafloor and of sparse volcanic formations. Our findings are consistent with the flip-flop detachment hypothesis proposed for this area by Sauter et al. (Nature Geosciences, 2013; ultramafic seafloor forming in the footwall of successive detachment faults, each cutting into the footwall of the previous fault, with an opposite polarity). Our observations also document the extent and geometry of deformation in the footwall of a young axial detachment, the role of mass-wasting for the evolution of this detachment, and provide spectacular evidence for serpentinization-related hydrothermal circulation and for spatial links between faults and volcanic eruptions.

  20. 77 FR 9652 - Proposed CERCLA Administrative Cost Recovery Settlement; Lake Linden Superfund Site in Lake...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-02-17

    ... Settlement; Lake Linden Superfund Site in Lake Linden, Houghton County, MI AGENCY: Environmental Protection... concerning the Lake Linden Superfund Site in Lake Linden, Houghton County, Michigan with Honeywell Specialty...-6609. Comments should reference the Lake Linden Superfund Site in Lake Linden, Houghton County...

  1. Long-term simulations of dissolved oxygen concentrations in Lake Trout lakes

    NASA Astrophysics Data System (ADS)

    Jabbari, A.; Boegman, L.; MacKay, M.; Hadley, K.; Paterson, A.; Jeziorski, A.; Nelligan, C.; Smol, J. P.

    2016-02-01

    Lake Trout are a rare and valuable natural resource that are threatened by multiple environmental stressors. With the added threat of climate warming, there is growing concern among resource managers that increased thermal stratification will reduce the habitat quality of deep-water Lake Trout lakes through enhanced oxygen depletion. To address this issue, a three-part study is underway, which aims to: analyze sediment cores to understand the past, develop empirical formulae to model the present and apply computational models to forecast the future. This presentation reports on the computational modeling efforts. To this end, a simple dissolved oxygen sub-model has been embedded in the one-dimensional bulk mixed-layer thermodynamic Canadian Small Lake Model (CSLM). This model is currently being incorporated into the Canadian Land Surface Scheme (CLASS), the primary land surface component of Environment Canada's global and regional climate modelling systems. The oxygen model was calibrated and validated by hind-casting temperature and dissolved oxygen profiles from two Lake Trout lakes on the Canadian Shield. These data sets include 5 years of high-frequency (10 s to 10 min) data from Eagle Lake and 30 years of bi-weekly data from Harp Lake. Initial results show temperature and dissolved oxygen was predicted with root mean square error <1.5 °C and <3 mgL-1, respectively. Ongoing work is validating the model, over climate-change relevant timescales, against dissolved oxygen reconstructions from the sediment cores and predicting future deep-water temperature and dissolved oxygen concentrations in Canadian Lake Trout lakes under future climate change scenarios. This model will provide a useful tool for managers to ensure sustainable fishery resources for future generations.

  2. A Dynamical Downscaling study over the Great Lakes Region Using WRF-Lake: Historical Simulation

    NASA Astrophysics Data System (ADS)

    Xiao, C.; Lofgren, B. M.

    2014-12-01

    As the largest group of fresh water bodies on Earth, the Laurentian Great Lakes have significant influence on local and regional weather and climate through their unique physical features compared with the surrounding land. Due to the limited spatial resolution and computational efficiency of general circulation models (GCMs), the Great Lakes are geometrically ignored or idealized into several grid cells in GCMs. Thus, the nested regional climate modeling (RCM) technique, known as dynamical downscaling, serves as a feasible solution to fill the gap. The latest Weather Research and Forecasting model (WRF) is employed to dynamically downscale the historical simulation produced by the Geophysical Fluid Dynamics Laboratory-Coupled Model (GFDL-CM3) from 1970-2005. An updated lake scheme originated from the Community Land Model is implemented in the latest WRF version 3.6. It is a one-dimensional mass and energy balance scheme with 20-25 model layers, including up to 5 snow layers on the lake ice, 10 water layers, and 10 soil layers on the lake bottom. The lake scheme is used with actual lake points and lake depth. The preliminary results show that WRF-Lake model, with a fine horizontal resolution and realistic lake representation, provides significantly improved hydroclimates, in terms of lake surface temperature, annual cycle of precipitation, ice content, and lake-effect snowfall. Those improvements suggest that better resolution of the lakes and the mesoscale process of lake-atmosphere interaction are crucial to understanding the climate and climate change in the Great Lakes region.

  3. Survival of lake trout eggs and fry reared in water from the upper Great Lakes

    USGS Publications Warehouse

    Mac, Michael J.; Edsall, Carol Cotant; Seelye, James G.

    1985-01-01

    As part of continuing studies of the reproductive failure of lake trout (Salvelinus namaycush) in Lake Michigan, we measured the survival of lake trout eggs and fry of different origins and reared in different environments. Eggs and milt were stripped from spawning lake trout collected in the fall of 1980 from southeastern Lake Michigan, northwestern Lake Huron, south central Lake Superior, and from hatchery brood stock. Eggs from all sources were incubated, and the newly hatched fry were reared for 139 days in lake water from each of the three upper Great Lakes and in well water. Survival of eggs to hatching at all sites was lowest for those from Lake Michigan (70% of fertilized eggs) and highest for eggs from Lake Superior (96%). Comparisons of incubation water from the different lakes indicated that hatching success of eggs from all sources was highest in Lake Huron water, and lowest in Lake Michigan water. The most notable finding was the nearly total mortality of fry from eggs of southeastern Lake Michigan lake trout. At all sites, the mean survival of Lake Michigan fry through 139 days after hatching was only 4% compared to near 50% for fry from the other three sources. In a comparison of the rearing sites, little influence of water quality on fry survival was found. Thus, the poor survival was associated with the source of eggs and sperm, not the water in which the fry were reared.

  4. Curiosity at Vera Rubin Ridge: Testable Hypotheses, First Results, and Implications for Habitability

    NASA Astrophysics Data System (ADS)

    Fraeman, A.; Bedford, C.; Bridges, J.; Edgar, L. A.; Hardgrove, C.; Horgan, B. H. N.; Gabriel, T. S. J.; Grotzinger, J. P.; Gupta, S.; Johnson, J. R.; Rampe, E. B.; Morris, R. V.; Salvatore, M. R.; Schwenzer, S. P.; Stack, K.; Pinet, P. C.; Rubin, D. M.; Weitz, C. M.; Wellington, D. F.; Wiens, R. C.; Williams, A. J.; Vasavada, A. R.

    2017-12-01

    As of sol 1756, Curiosity was 250 meters from ascending Vera Rubin Ridge, a unique geomorphic feature preserved in the lower foothills of Aeolis Mons (informally known as Mt. Sharp) that is distinguishable from orbit. Vera Rubin Ridge (previously termed the Hematite Ridge) is characterized by a higher thermal inertia than the surrounding terrain, is comparatively resistant to erosion, and is capped with a hematite-bearing layer that is visible in 18 m/pixel CRISM data. A key hypothesis associated with this unit is that it represents a redox interface where ferrous iron oxidized and precipitated either as hematite or another ferric precursor. The Curiosity integrated payload is being used to determine the depositional environment(s), stratigraphic context and geochemical conditions associated with this interface, all of which will provide key insights into its past habitability potential and the relative timing of processes. Specifically, analysis of Curiosity data will address four major questions related to the history and evolution of ridge-forming strata: (1) What is the stratigraphic relationship between the units in the ridge and the Mt. Sharp group (see Grotzinger et al., 2015)? (2) What primary and secondary geologic processes deposited and modified the ridge units over time? (3) What is the nature and timing of the hematite precipitation environment, and how does it relate to similar oxidized phases in the Murray formation? (4) What are the implications for habitability and the preservation of organic molecules? Initial results of a systematic imaging campaign along the contact between the lower portion or the ridge and the Murray formation has revealed dm-scale cross bedding within the ridge stratigraphy, which provide clues about the depositional environments; these can be compared to suites of sedimentary structures within the adjacent Murray formation. Long distance ChemCam passive and Mastcam multispectral data show that hematite and likely other

  5. Ridge-like lava tube systems in southeast Tharsis, Mars

    NASA Astrophysics Data System (ADS)

    Zhao, Jiannan; Huang, Jun; Kraft, Michael D.; Xiao, Long; Jiang, Yun

    2017-10-01

    Lava tubes are widely distributed in volcanic fields on a planetary surface and they are important means of lava transportation. We have identified 38 sinuous ridges with a lava-tube origin in southeast Tharsis. The lengths vary between 14 and 740 km, and most of them occur in areas with slopes < 0.3°. We analyzed their geomorphology in detail with CTX (Context Camera) and HiRISE (High Resolution Imaging Science Experiment) images and DTM (digital terrain model) derived from them. We identified three cross-sectional shapes of these sinuous ridges: round-crested, double-ridged, and flat-crested and described features associated with the lava tubes, including branches, axial cracks, collapsed pits, breakout lobes, and tube-fed lava deltas. Age determination results showed that most of the lava tubes formed in Late Hesperian and were active until the Hesperian-Amazonian boundary. We proposed that these lava tubes formed at relatively low local flow rate, low lava viscosity, and sustained magma supply during a long period. Besides, lava flow inflation is also important in the formation of the ridge-like lava tubes and some associated features. These lava tubes provide efficient lateral pathways for magma transportation over the relatively low topographic slopes in southeast Tharsis, and they are important for the formation of long lava flows in this region. The findings of this study provide an alternative formation mechanism for sinuous ridges on the martian surface.

  6. Basalts dredged from the Amirante ridge, western Indian ocean

    USGS Publications Warehouse

    Fisher, R.L.; Engel, C.G.; Hilde, T.W.C.

    1968-01-01

    Oceanic tholeiitic basalts were dredged from 2500 to 3000 m depth on each flank of the Amirante Ridge, 1200 km southeast of Somalia in the western Indian Ocean, by R.V. Argo in 1964. One sample, probably shed from a flow or dike in basement beneath the coralline cap, gave a wholerock KAr age of 82??16??106 years. The age is similar to those reported by others for agglomerate from Providence Reef, nearer Madagascar, and for gabbro from Chain Ridge, the southwest member of Owen Fracture Zone, nearer the Somali coast. The Amirante Cretaceous-Early Tertiary occurrence lies between the "continental" 650 ?? 106 years granites of Seychelles Archipelago and the large Precambrian "continental" block of Madagascar. Trends of major structures and distribution of the related topographic and magnetic-anomaly lineations in 7-8 ?? 106 km2of the surrounding Indian Ocean suggest that in addition to spreading of the seafloor from the seismically-active Mid-Indian Ocean Ridge-Carlsberg Ridge complex there has been, since mid-Mesozoic time, distributed left-lateral shear along 52??-54??E that has moved Madagascar at least 700 km south relative to Seychelles Bank. Measurements by other indicate the absolute movement of Madagascar has been southward as well. The emplacement of oceanic tholeiitic basalts at shallow depth, the development of volcanic topography between the sedimented Somali and Mascarene basins, and the existence of the faulted Amirante Trench and Ridge are consequences of the displacement. ?? 1968.

  7. The most acidified Austrian lake in comparison to a neutralized mining lake

    PubMed Central

    Moser, Michael; Weisse, Thomas

    2011-01-01

    This study investigated two mining lakes located in the north of Lower Austria. These lakes arose 45 years ago when open cast lignite mining ceased. The lakes are separated by a 7-m wide dam. Due to the oxidation of pyrite, both lakes have been acidified and exhibit iron, sulphate, and heavy metal concentrations several orders of magnitude higher than in circumneutral lakes. The water column of both lakes is divided into two layers by a pronounced chemocline. The smaller mining lake (AML), with pH close to of 2.6, is the most acidic lake in Austria, whereas flooding with stream water and by drainage from the surrounding fields neutralized the adjacent larger pit lake. The goal of our study was to investigate the effect of flooding on its physical, chemical and biological properties, in comparison to the pristine AML. Even relative to other extremely acidic lakes, the flora and fauna in the AML was reduced and composed of only two flagellate, one ciliate, and one rotifer species. The simplified pelagic food web in the mixolimnion consisted of heterotrophic bacteria, the mixotrophic flagellates Chlamydomonas acidophila and Ochromonas sp., the ciliate Oxytricha sp., and the rotifer Cephalodella sp. The latter two are as yet undescribed new species. The heliozoan Actinophrys sp. that may act as top predator occurred only in low abundance. The euglenid Lepocinclis buetschlii formed a stable deep chlorophyll maximum (DCM) at 7 m depth. Highest cell numbers of L. buetschlii in the DCM exceeded 108 L−1. The neutralized mining lake harboured higher plankton diversity similar to that of natural circumneutral lakes. A peak of at least 16 different phytoplankton taxa was observed during summer. The zooplankton consisted of several copepod species, daphnids and other cladocerans, and at least six different rotifer species. Several fish species occurred in the neutralized lake. Although the effect of non-permanent flooding was largely sustainable, interannual fluctuations of

  8. Hydrodynamic role of longitudinal dorsal ridges in a leatherback turtle swimming

    NASA Astrophysics Data System (ADS)

    Bang, Kyeongtae; Kim, Jooha; Lee, Sang-Im; Choi, Haecheon

    2016-10-01

    Leatherback sea turtles (Dermochelys coriacea) are known to have a superior diving ability and be highly adapted to pelagic swimming. They have five longitudinal ridges on their carapace. Although it was conjectured that these ridges might be an adaptation for flow control, no rigorous study has been performed to understand their hydrodynamic roles. Here we show that these ridges are slightly misaligned to the streamlines around the body to generate streamwise vortices, and suppress or delay flow separation on the carapace, resulting in enhanced hydrodynamic performances during different modes of swimming. Our results suggest that shapes of some morphological features of living creatures, like the longitudinal ridges of the leatherback turtles, need not be streamlined for excellent hydro- or aerodynamic performances, contrary to our common physical intuition.

  9. Near-ridge seamount chains in the northeastern Pacific Ocean

    NASA Astrophysics Data System (ADS)

    Clague, David A.; Reynolds, Jennifer R.; Davis, Alicé S.

    2000-07-01

    High-resolution bathymetry and side-scan data of the Vance, President Jackson, and Taney near-ridge seamount chains in the northeast Pacific were collected with a hull-mounted 30-kHz sonar. The central volcanoes in each chain consist of truncated cone-shaped volcanoes with steep sides and nearly flat tops. Several areas are characterized by frequent small eruptions that result in disorganized volcanic regions with numerous small cones and volcanic ridges but no organized truncated conical structure. Several volcanoes are crosscut by ridge-parallel faults, showing that they formed within 30-40 km of the ridge axis where ridge-parallel faulting is still active. Magmas that built the volcanoes were probably transported through the crust along active ridge-parallel faults. The volcanoes range in volume from 11 to 187 km3, and most have one or more multiple craters and calderas that modify their summits and flanks. The craters (<1 km diameter) and calderas (>1 km diameter) range from small pit craters to calderas as large as 6.5×8.5 km, although most are 2-4 km across. Crosscutting relationships commonly show a sequence of calderas stepping toward the ridge axis. The calderas overlie crustal magma chambers at least as large as those that underlie Kilauea and Mauna Loa Volcanoes in Hawaii, perhaps 4-5 km in diameter and ˜1-3 km below the surface. The nearly flat tops of many of the volcanoes have remnants of centrally located summit shields, suggesting that their flat tops did not form from eruptions along circumferential ring faults but instead form by filling and overflowing of earlier large calderas. The lavas retain their primitive character by residing in such chambers for only short time periods prior to eruption. Stored magmas are withdrawn, probably as dikes intruded into the adjacent ocean crust along active ridge-parallel faults, triggering caldera collapse, or solidified before the next batch of magma is intruded into the volcano, probably 1000-10,000 years

  10. 7 CFR 354.2 - Administrative instructions prescribing commuted traveltime.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... (including Port Allen) 2 Buras New Orleans 4 Burnside Baton Rouge 3 Cameron Lake Charles 3 Carlyss Lake Charles 2 Clifton Ridge Lake Charles 2 Convent Baton Rouge 3 Donaldsonville Baton Rouge 3 England Air Park... Baton Rouge 2 Hackberry Lake Charles 2 Lake Charles Baton Rouge 5 Lake Charles Port Arthur, TX 3 Lake...

  11. Seismic Data Reveal Lake-Level Changes in Lake Issyk-Kul, Kyrgyzstan

    NASA Astrophysics Data System (ADS)

    Gebhardt, C.; Spiess, V.; Keil, H.; Sauermilch, I.; Oberhänsli, H.; Abdrakhmatov, K.; De Batist, M. A.; Naudts, L.; De Mol, L.

    2013-12-01

    Lake Issyk-Kul is located in an intramontane basin of the Tien Shan, Kyrgyzstan, Central Asia, at 1607 m above sea level. It has formed in a tectonically active region with W-E striking major thrust zones both N and S of the lake. The lake is elongated with 180 km in W-E and 60 km in S-N direction and a water depth of roughly 670 m at its central plain. With a surface area of 6232 km2 and a total water colume of around 1736 km3, Lake Issyk-Kul is the second largest lake in the higher altitudes (De Batist et al., 2002). Two large delta areas have formed at the E and W end. Steep slopes at both the N and S shore separate rather narrow, shallow shelf areas from the central deeper plain. First seismic data of lake Issyk-Kul were acquired in 1982 by the Moscow University with a total of 31 profiles across the lake. In 1997 and 2001, a second and third seismic survey of the lake were carried out by the group of Marc De Batist (Ghent, Belgium) in cooperation with the Royal Museum of Central Africa (Tervuren, Belgium) and the SBRAS (Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia) using a sparker system with a single-channel streamer. These surveys were recently completed by a fourth expedition carried out by the University of Bremen in April 2013. During this expedition, 33 additional profiles were acquired with an airgun and a multi-channel streamer. The sparker surveys mostly cover the delta and shelf areas in high detail, while the airgun survey covers the deeper parts of the lake with penetration beyond the first multiple. Bathymetry data reveal that at the delta areas, the shelf is divided into two parts. The shallower comprises the part down to 110 m water depth with an average inclination of 0.5°, while the deeper part reaches from 110 m to 300 m water depth with an average slope inclination of 1°. Incised paleo-river channels of up to 2-3 km width and 50 m depth are visible both on the eastern and western shelf, but are limited to the

  12. Salting our freshwater lakes.

    PubMed

    Dugan, Hilary A; Bartlett, Sarah L; Burke, Samantha M; Doubek, Jonathan P; Krivak-Tetley, Flora E; Skaff, Nicholas K; Summers, Jamie C; Farrell, Kaitlin J; McCullough, Ian M; Morales-Williams, Ana M; Roberts, Derek C; Ouyang, Zutao; Scordo, Facundo; Hanson, Paul C; Weathers, Kathleen C

    2017-04-25

    The highest densities of lakes on Earth are in north temperate ecosystems, where increasing urbanization and associated chloride runoff can salinize freshwaters and threaten lake water quality and the many ecosystem services lakes provide. However, the extent to which lake salinity may be changing at broad spatial scales remains unknown, leading us to first identify spatial patterns and then investigate the drivers of these patterns. Significant decadal trends in lake salinization were identified using a dataset of long-term chloride concentrations from 371 North American lakes. Landscape and climate metrics calculated for each site demonstrated that impervious land cover was a strong predictor of chloride trends in Northeast and Midwest North American lakes. As little as 1% impervious land cover surrounding a lake increased the likelihood of long-term salinization. Considering that 27% of large lakes in the United States have >1% impervious land cover around their perimeters, the potential for steady and long-term salinization of these aquatic systems is high. This study predicts that many lakes will exceed the aquatic life threshold criterion for chronic chloride exposure (230 mg L -1 ), stipulated by the US Environmental Protection Agency (EPA), in the next 50 y if current trends continue.

  13. Morphometry and mixing regime of a tropical lake: Lake Nova (Southeastern Brazil).

    PubMed

    Gonçalves, Monica A; Garcia, Fábio C; Barroso, Gilberto F

    2016-09-01

    Lake Nova (15.5 km2) is the second largest lake in the Lower Doce River Valley (Southeastern Brazil). A better understanding of ecosystem structure and functioning requires knowledge about lake morphometry, given that lake basin form influences water column stratification. The present study aims to contribute to the understanding of relationship between morphometry and mixing patterns of deep tropical lakes in Brazil. Water column profiles of temperature and dissolved oxygen were taken on four sampling sites along the lake major axis during 2011, 2012 and 2013. The bathymetric survey was carried out in July 2011, along 131.7 km of hydrographic tracks yield 51,692 depth points. Morphometric features of lake size and form factors describe the relative deep subrectangular elongated basin with maximum length of 15.7 km, shoreline development index 5.0, volume of 0.23 km3, volume development of 1.3, and maximum, mean and relative depths of 33.9 m, 14.7 m and 0.7 %, respectively. The deep basin induces a monomictic pattern, with thermal stratification during the wet/warm season associated with anoxic bottom waters (1/3 of lake volume), and mixing during dry and cool season. Based on in situ measurements of tributary river discharges, theoretical retention time (RT) has been estimated in 13.4 years. The morphometry of Lake Nova promote long water RT and the warm monomictic mixing pattern, which is in accordance to the deep tropical lakes in Brazil.

  14. Characterization of Lake Michigan coastal lakes using zooplankton assemblages

    USGS Publications Warehouse

    Whitman, Richard L.; Nevers, Meredith B.; Goodrich, Maria L.; Murphy, Paul C.; Davis, Bruce M.

    2004-01-01

    Zooplankton assemblages and water quality were examined bi-weekly from 17 April to 19 October 1998 in 11 northeastern Lake Michigan coastal lakes of similar origin but varied in trophic status and limnological condition. All lakes were within or adjacent to Sleeping Bear Dunes National Lakeshore, Michigan. Zooplankton (principally microcrustaceans and rotifers) from triplicate Wisconsin net (80 I?m) vertical tows taken at each lake's deepest location were analyzed. Oxygen-temperature-pH-specific conductivity profiles and surface water quality were concurrently measured. Bray-Curtis similarity analysis showed small variations among sample replicates but large temporal differences. The potential use of zooplankton communities for environmental lake comparisons was evaluated by means of BIOENV (Primer 5.1) and principal component analyses. Zooplankton analyzed at the lowest identified taxonomic level yielded greatest sensitivity to limnological variation. Taxonomic and ecological aggregations of zooplankton data performed comparably, but less well than the finest taxonomic analysis. Secchi depth, chlorophyll a, and sulfate concentrations combined to give the best correlation with patterns of variation in the zooplankton data set. Principal component analysis of these variables revealed trophic status as the most influential major limnological gradient among the study lakes. Overall, zooplankton abundance was an excellent indicator of variation in trophic status.

  15. The study of fresh-water lake ice using multiplexed imaging radar

    USGS Publications Warehouse

    Leonard, Bryan M.; Larson, R.W.

    1975-01-01

    The study of ice in the upper Great Lakes, both from the operational and the scientific points of view, is receiving continued attention. Quantitative and qualitative field work is being conducted to provide the needed background for accurate interpretation of remotely sensed data. The data under discussion in this paper were obtained by a side-looking multiplexed airborne radar (SLAR) supplemented with ground-truth data.Because of its ability to penetrate adverse weather, radar is an especially important instrument for monitoring ice in the upper Great Lakes. It has previously been shown that imaging radars can provide maps of ice cover in these areas. However, questions concerning both the nature of the surfaces reflecting radar energy and the interpretation of the radar imagery continually arise.Our analysis of ice in Whitefish Bay (Lake Superior) indicates that the combination of the ice/water interlace and the ice/air interface is the major contributor to the radar backscatter as seen on the imagery At these frequencies the ice has a very low relative dielectric permittivity (< 3.0) and a low loss tangent Thus, this ice is somewhat transparent to the energy used by the imaging SLAR system. The ice types studied include newly formed black ice, pancake ice, and frozen and consolidated pack and brash ice.Although ice thickness cannot be measured directly from the received signals, it is suspected that by combining the information pertaining to radar backscatter with data on the meteorological and sea-state history of the area, together with some basic ground truth, better estimates of the ice thickness may be provided. In addition, certain ice features (e.g. ridges, ice-foot formation, areas of brash ice) may be identified with reasonable confidence. There is a continued need for additional ground work to verify the validity of imaging radars for these types of interpretations.

  16. Lake Tahoe

    EPA Pesticide Factsheets

    Information on the Lake Tahoe watershed, EPA's protection efforts, water quality issues, effects of climate change, Lake Tahoe Total Maximum Daily Load (TMDL), EPA-sponsored projects, list of partner agencies.

  17. Evidence of recent volcanic activity on the ultraslow-spreading Gakkel ridge.

    PubMed

    Edwards, M H; Kurras, G J; Tolstoy, M; Bohnenstiehl, D R; Coakley, B J; Cochran, J R

    2001-02-15

    Seafloor spreading is accommodated by volcanic and tectonic processes along the global mid-ocean ridge system. As spreading rate decreases the influence of volcanism also decreases, and it is unknown whether significant volcanism occurs at all at ultraslow spreading rates (<1.5 cm yr(-1)). Here we present three-dimensional sonar maps of the Gakkel ridge, Earth's slowest-spreading mid-ocean ridge, located in the Arctic basin under the Arctic Ocean ice canopy. We acquired this data using hull-mounted sonars attached to a nuclear-powered submarine, the USS Hawkbill. Sidescan data for the ultraslow-spreading (approximately 1.0 cm yr(-1)) eastern Gakkel ridge depict two young volcanoes covering approximately 720 km2 of an otherwise heavily sedimented axial valley. The western volcano coincides with the average location of epicentres for more than 250 teleseismic events detected in 1999, suggesting that an axial eruption was imaged shortly after its occurrence. These findings demonstrate that eruptions along the ultraslow-spreading Gakkel ridge are focused at discrete locations and appear to be more voluminous and occur more frequently than was previously thought.

  18. Geographical distributions of lake trout strains stocked in Lake Ontario

    USGS Publications Warehouse

    Elrod, Joseph H.; O'Gorman, Robert; Schneider, Clifford P.; Schaner, Ted

    1996-01-01

    Geographical distributions of lake trout (Salvelinus namaycush) stocked at seven locations in U.S. waters and at four locations in Canadian waters of Lake Ontario were determined from fish caught with gill nets in September in 17 areas of U.S. waters and at 10 fixed locations in Canadian waters in 1986-95. For fish of a given strain stocked at a given location, geographical distributions were not different for immature males and immature females or for mature males and mature females. The proportion of total catch at the three locations nearest the stocking location was higher for mature fish than for immature fish in all 24 available comparisons (sexes combined) and was greater for fish stocked as yearlings than for those stocked as fingerlings in all eight comparisons. Mature fish were relatively widely dispersed from stocking locations indicating that their tendency to return to stocking locations for spawning was weak, and there was no appreciable difference in this tendency among strains. Mature lake trout were uniformly distributed among sampling locations, and the strain composition at stocking locations generally reflected the stocking history 5 to 6 years earlier. Few lake trout moved across Lake Ontario between the north and south shores or between the eastern outlet basin and the main lake basin. Limited dispersal from stocking sites supports the concept of stocking different genetic strains in various parts of the lake with the attributes of each strain selected to match environmental conditions in the portion of the lake where it is stocked.

  19. Deglaciation, lake levels, and meltwater discharge in the Lake Michigan basin

    USGS Publications Warehouse

    Colman, Steven M.; Clark, J.A.; Clayton, L.; Hansel, A.K.; Larsen, C.E.

    1994-01-01

    The deglacial history of the Lake Michigan basin, including discharge and routing of meltwater, is complex because of the interaction among (1) glacial retreats and re-advances in the basin (2) the timing of occupation and the isostatic adjustment of lake outlets and (3) the depositional and erosional processes that left evidence of past lake levels. In the southern part of the basin, a restricted area little affected by differential isostasy, new studies of onshore and offshore areas allow refinement of a lake-level history that has evolved over 100 years. Important new data include the recognition of two periods of influx of meltwater from Lake Agassiz into the basin and details of the highstands gleaned from sedimentological evidence. Major disagreements still persist concerning the exact timing and lake-level changes associated with the Algonquin phase, approximately 11,000 BP. A wide variety of independent data suggests that the Lake Michigan Lobe was thin, unstable, and subject to rapid advances and retreats. Consequently, lake-level changes were commonly abrupt and stable shorelines were short-lived. The long-held beliefs that the southern part of the basin was stable and separated from deformed northern areas by a hinge-line discontinuity are becoming difficult to maintain. Numerical modeling of the ice-earth system and empirical modeling of shoreline deformation are both consistent with observed shoreline tilting in the north and with the amount and pattern of modern deformation shown by lake-level gauges. New studies of subaerial lacustrine features suggest the presence of deformed shorelines higher than those originally ascribed to the supposed horizontal Glenwood level. Finally, the Lake Michigan region as a whole appears to behave in a similar manner to other areas, both local (other Great Lakes) and regional (U.S. east coast), that have experienced major isostatic changes. Detailed sedimentological and dating studies of field sites and additional

  20. Feature Selection for Ridge Regression with Provable Guarantees.

    PubMed

    Paul, Saurabh; Drineas, Petros

    2016-04-01

    We introduce single-set spectral sparsification as a deterministic sampling-based feature selection technique for regularized least-squares classification, which is the classification analog to ridge regression. The method is unsupervised and gives worst-case guarantees of the generalization power of the classification function after feature selection with respect to the classification function obtained using all features. We also introduce leverage-score sampling as an unsupervised randomized feature selection method for ridge regression. We provide risk bounds for both single-set spectral sparsification and leverage-score sampling on ridge regression in the fixed design setting and show that the risk in the sampled space is comparable to the risk in the full-feature space. We perform experiments on synthetic and real-world data sets; a subset of TechTC-300 data sets, to support our theory. Experimental results indicate that the proposed methods perform better than the existing feature selection methods.

  1. 77 FR 39638 - Safety Zone; Barbara Harder Wedding Fireworks, Lake Erie, Lake View, NY

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-07-05

    ...-AA00 Safety Zone; Barbara Harder Wedding Fireworks, Lake Erie, Lake View, NY AGENCY: Coast Guard, DHS. ACTION: Temporary final rule. SUMMARY: The Coast Guard is establishing a temporary safety zone on Lake Erie, Lake View, NY. This safety zone is intended to restrict vessels from a portion of Lake Erie...

  2. Subsidence and volcanism of the Haleakala Ridge, Hawaii

    USGS Publications Warehouse

    Moore, J.G.; Clague, D.A.; Ludwig, K. R.; Mark, R.K.

    1990-01-01

    Side-looking sonar (GLORIA) mapping has revealed a series of four arcuate bands of high sonic backscatter on the crest of the Haleakala Ridge, a major rift-zone ridge extending 135 km east of the island of Maui. Dredge recovery indicates that the shallowest of these bands is a drowned coral reef, and the deeper bands are also inferred to be coral reefs. The reefs occur above a prominent submarine bench 1500-2500 m deep on the ridge (H-terrace) that marks the shoreline at the end of vigorous shield building of Haleakala volcano when lava flows ceased crossing and reworking the shoreline. Since their growth these reefs have subsided as much as 2200 m and have tilted systematically about 20 m/km southward as a result of post-reef volcanic loading on the island of Hawaii, whose center of mass is about directly south of the Haleakala Ridge. The 234U/238U age of the dredged coral is 750 ?? 13 ka, in reasonable agreement with an age of 850 ka for the underlying H terrace previously estimated from its relationship to other dated reefs to the southwest. Basalt glass fragments dredged from the Haleakala Ridge below the H terrace are tholeiitic and contain high sulfur indicative of eruption in water deeper than 200 m. Basalt glass fragments associated with the reefs above the H terrace are dominantly tholeiitic and contain intermediate sulfur contents, indicative of subaqueous eruption in shallow, near-shore conditions. One alkalic glass fragment was recovered above the H terrace. These relations indicate that the morphologic end of shield building as recorded by construction of the H terrace was not accompanyed by a change from tholeiitic to alkalic basalt; instead tholeiite eruptions continued for some time before the erupted lava became alkalic. ?? 1990.

  3. Genetic diversity of lake whitefish in lakes Michigan and Huron: sampling, standardization, and research priorities

    USGS Publications Warehouse

    Stott, Wendylee; VanDeHey, Justin A.; Sloss, Brian L.

    2010-01-01

    We combined data from two laboratories to increase the spatial extent of a genetic data set for lake whitefish Coregonus clupeaformis from lakes Huron and Michigan and saw that genetic diversity was greatest between lakes, but that there was also structuring within lakes. Low diversity among stocks may be a reflection of relatively recent colonization of the Great Lakes, but other factors such as recent population fluctuation and localized stresses such as lamprey predation or heavy exploitation may also have a homogenizing effect. Our data suggested that there is asymmetrical movement of lake whitefish between Lake Huron and Lake Michigan; more genotypes associated with Lake Michigan were observed in Lake Huron. Adding additional collections to the calibrated set will allow further examination of diversity in other Great Lakes, answer questions regarding movement among lakes, and estimate contributions of stocks to commercial yields. As the picture of genetic diversity and population structure of lake whitefish in the Great Lakes region emerges, we need to develop methods to combine data types to help identify important areas for biodiversity and thus conservation. Adding genetic data to existing models will increase the precision of predictions of the impacts of new stresses and changes in existing pressures on an ecologically and commercially important species.

  4. [Characterizing chromophoric dissolved organic matter (CDOM) in Lake Honghu, Lake Donghu and Lake Liangzihu using excitation-emission matrices (EEMs) fluorescence and parallel factor analysis (PARAFAC)].

    PubMed

    Zhou, Yong-Qiang; Zhang, Yun-Lin; Niu, Cheng; Wang, Ming-Zhu

    2013-12-01

    Little is known about DOM characteristics in medium to large sized lakes located in the middle and lower reaches of Yangtze River, like Lake Honghu, Lake Donghu and Lake Liangzihu. Absorption, fluorescence and composition characteristics of chromophoric dissolved organic matter (CDOM) are presented using the absorption spectroscopy, the excitation-emission ma trices (EEMs) fluorescence and parallel factor analysis (PARAFAC) model based on the data collected in Sep-Oct. 2007 including 15, 9 and 10 samplings in Lake Honghu, Lake Donghu and Lake Liangzihu, respectively. CDOM absorption coefficient at 350 nm a(350) coefficient in Lake Honghu was significantly higher than those in Lake Donghu and Lake Liangzihu (t-test, p< 0. 001). A significant negative correlation was found between CDOM spectral slope in the wavelength range of 280-500 nm (S280-500) and a(350) (R2 =0. 781, p<0. 001). The mean value of S280-500 in Lake Honghu was significantly lower than those in Lake Donghu (t-test, pLake Liangzihu (t-test, p<0. 001). The mean value of spectral slope ratio SR in Lake Honghu was also significantly lower than those in Lake Donghu and Lake Liangzihu (t-test, p<0. 05). Two humic-like (C1, C2) and two protein-like fluorescent components (C3, C4) were identified by PARAFAC model, among which significant positive correlations were found between C1 and C2 (R2 =0. 884, p<0. 001), C3 and C4 (R2 =0. 677, p<0.001), respectively, suggesting that the sources of the two humic-like components as well as the two protein-like components were similar. However, no significant correlation has been found between those 4 fluorescent components and DOC concentration. Th e fluorescenceindices of FI255 (HIX), Fl265, FI310 (BIX) and Fl370 in Lake Donghu were all significantly higher than those in Lake Liangzihu (t-test, p <0.05) and Lake Honghu (t-test, p<0. 01), indicating that the eutrophication status in Lake Donghu was higher than Lake Honghu and Lake Liangzihu.

  5. Olivine-Rich Troctolite from the Southwest Indian Ridge: Constrains on Melt-Rock Reaction beneath Mid-Ocean Ridges

    NASA Astrophysics Data System (ADS)

    Yang, A. Y.

    2017-12-01

    The origin of olivine-rich troctolite, which have been recovered in the plutonic sample suites from the fast-spreading East Pacific Rise, and slow-spreading Mid-Atlantic Ridge and Central Indian Ridge, has been highly debated. They can form either by fractionation of primitive mid-ocean ridge basalt (MORB) melts or by melt migrating through pre-existing (possibly mantle) olivine matrix, thus recording valuable information of magmatic process at mantle-crust transition. This study presents in situ major and trace element study on the olivine-rich troctolite first reported from the ultraslow-spreading Southwest Indian Ridge (SWIR), together with a series of samples from peridotite, gabbro to basalt from an amagmatic segment at 53°E during Dayangyihao Cruises, to investigate the magmatic processes occurred at mantle-crust transition and origin of olivine-rich troctolite. The olivine in the troctolite shows cumulate textures with interstitial clinopyroxene, plagioclase and minor spinel, which is cross-cut by an olivine gabbro vein. Olivine in the troctolite show only mildly decreasing NiO contents (from 0.31-0.25 wt.%) with decreasing Fo (from 86 to 81), and even olivine in the gabbro have NiO up to 0.24 wt.% with Fo of 75. The Fo vs. Ni correlation of olivine is shifted to uniquely higher NiO at a certain Fo compared to the trends defined by either olivine from other lower oceanic crust (LOC) cumulates worldwide or olivine compositions from classic fractionation model for primitive MORB magma. Interstitial clinopyroxene in the troctolite have high Mg# (88-90), Cr2O3 (up to 1.51 wt.%) and TiO2 contents (up to 1.01 wt.%) with Eu/Eu* from 0.4-0.6. Such high-Ti-Cr-Mg# clinopyroxene is rare among global LOC cumulates, and cannot result from simple fractionation of MORB magma. The mineral compositions in the olivine-rich troctolite could be modeled by reaction between a primitive olivine matrix and a highly evolved melt (with 2.4 wt.% TiO2), and such a melt composition is

  6. Exploring trends, causes, and consequences of declining lipids in Lake Superior lake trout

    EPA Science Inventory

    The ability of lake trout to forage in deepwater habitats is facilitated by high lipid content, which affords buoyancy. In Lake Superior, lean lake trout historically occupied depths < 80 m, and siscowet lake trout occupied depths > 80 m. Siscowets have been known f...

  7. Great Lakes

    USGS Publications Warehouse

    Edsall, Thomas A.; Mac, Michael J.; Opler, Paul A.; Puckett Haecker, Catherine E.; Doran, Peter D.

    1998-01-01

    The Great Lakes region, as defined here, includes the Great Lakes and their drainage basins in Minnesota, Wisconsin, Illinois, Indiana, Ohio, Pennsylvania, and New York. The region also includes the portions of Minnesota, Wisconsin, and the 21 northernmost counties of Illinois that lie in the Mississippi River drainage basin, outside the floodplain of the river. The region spans about 9º of latitude and 20º of longitude and lies roughly halfway between the equator and the North Pole in a lowland corridor that extends from the Gulf of Mexico to the Arctic Ocean.The Great Lakes are the most prominent natural feature of the region (Fig. 1). They have a combined surface area of about 245,000 square kilometers and are among the largest, deepest lakes in the world. They are the largest single aggregation of fresh water on the planet (excluding the polar ice caps) and are the only glacial feature on Earth visible from the surface of the moon (The Nature Conservancy 1994a).The Great Lakes moderate the region’s climate, which presently ranges from subarctic in the north to humid continental warm in the south (Fig. 2), reflecting the movement of major weather masses from the north and south (U.S. Department of the Interior 1970; Eichenlaub 1979). The lakes act as heat sinks in summer and heat sources in winter and are major reservoirs that help humidify much of the region. They also create local precipitation belts in areas where air masses are pushed across the lakes by prevailing winds, pick up moisture from the lake surface, and then drop that moisture over land on the other side of the lake. The mean annual frost-free period—a general measure of the growing-season length for plants and some cold-blooded animals—varies from 60 days at higher elevations in the north to 160 days in lakeshore areas in the south. The climate influences the general distribution of wild plants and animals in the region and also influences the activities and distribution of the human

  8. Oak Ridge Reservation Annual Site environmental report summary for 1994

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    NONE

    1995-09-01

    This document presents a summary of the information collected for the Oak Ridge Reservation 1994 site environmental report. Topics discussed include: Oak Ridge Reservation mission; ecology; environmental laws; community participation; environmental restoration; waste management; radiation effects; chemical effects; risk to public; environmental monitoring; and radionuclide migration.

  9. 133. View of rock cut at base of rough ridge ...

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

    133. View of rock cut at base of rough ridge and roadway crossing unnamed viaduct on Grandfather Mountain with the Great Wall of China supporting the curve in the distance. Looking southeast. - Blue Ridge Parkway, Between Shenandoah National Park & Great Smoky Mountains, Asheville, Buncombe County, NC

  10. Dielectrophoresis device and method having insulating ridges for manipulating particles

    DOEpatents

    Cummings, Eric B [Livermore, CA; Fiechtner, Gregory J [Livermore, CA

    2008-03-25

    Embodiments of the present invention provide methods and devices for manipulating particles using dielectrophoresis. Insulating ridges and valleys are used to generate a spatially non-uniform electrical field. Particles may be concentrated, separated, or captured during bulk fluid flow in a channel having insulating ridges and valleys.

  11. Lakes, Lagerstaetten, and Evolution

    NASA Astrophysics Data System (ADS)

    Kordesch, E. G.; Park, L. E.

    2001-12-01

    The diversity of terrestrial systems is estimated to be greater than in the marine realm. However no hard data yet exists to substantiate this claim. Ancient lacustrine deposits may preserve an exceptionally diverse fossil fauna and aid in determining continental faunal diversities. Fossils preserved in lake deposits, especially those with exceptional preservation (i.e. Konservat Lagerstaetten), may represent a dependable method for determining species diversity changes in the terrestrial environment because of their faunal completeness. Important Konservat Lagerstaetten, such as the Green River Formation (US) and Messel (Germany), both Eocene in age, are found in lake sediments and show a remarkable faunal diversity for both vertebrates and invertebrates. To date information from nearly 25 lake lagerstaetten derived from different types of lake basins from the Carboniferous to the Miocene have been collected and described. Carboniferous sites derive from the cyclothems of Midcontinent of the US while many Cenozoic sites have been described from North and South America as well as Europe and Australia. Asian sites contain fossils from the Mesozoic and Cenozoic. With this data, insight into the evolutionary processes associated with lake systems can be examined. Do lakes act as unique evolutionary crucibles in contrast to marine systems? The speciation of cichlid fishes in present-day African lakes appears to be very high and is attributed to the diversity of environments found in large rift lakes. Is this true of all ancient lakes or just large rift lakes? The longevity of a lake system may be an important factor in allowing speciation and evolutionary processes to occur; marine systems are limited only in the existence of environments as controlled by tectonics and sea level changes, on the order of tens of millions of years. Rift lakes are normally the longest lived in the millions of years. Perhaps there are only certain types of lakes in which speciation of

  12. Suspended-sediment budget, flow distribution, and lake circulation for the Fox Chain of Lakes in Lake and McHenry Counties, Illinois, 1997-99

    USGS Publications Warehouse

    Schrader, David L.; Holmes, Robert R.

    2000-01-01

    The Fox Chain of Lakes is a glacial lake system in McHenry and Lake Counties in northern Illinois and southern Wisconsin. Sedimentation and nutrient overloading have occurred in the lake system since the first dam was built (1907) in McHenry to raise water levels in the lake system. Using data collected from December 1, 1997, to June 1, 1999, suspended-sediment budgets were constructed for the most upstream lake in the system, Grass Lake, and for the lakes downstream from Grass Lake. A total of 64,900 tons of suspended sediment entered Grass Lake during the study, whereas a total of 70,600 tons of suspended sediment exited the lake, indicating a net scour of 5,700 tons of sediment. A total of 44,100 tons of suspended sediment was measured exiting the Fox Chain of Lakes at Johnsburg, whereas 85,600 tons entered the system downstream from Grass Lake. These suspended-sediment loads indicate a net deposition of 41,500 tons downstream from Grass Lake, which represents a trapping efficiency of 48.5 percent. A large amount of recreational boating takes place on the Fox Chain of Lakes during summer months, and suspended-sediment load was observed to rise from 110 tons per day to 339 tons per day during the 1999 Memorial Day weekend (May 26 ?31, 1999). Presumably, this rise was the result of the boating traffic because no other hydrologic event is known to have occurred that might have caused the rise. This study covers a relatively short period and may not represent the long-term processes of the Fox Chain of Lakes system, although the sediment transport was probably higher than an average year. The bed sediments found on the bottom of the lakes are composed of mainly fine particles in the silt-clay range. The Grass Lake sediments were characterized as black peat with an organic content of between 9 and 18 percent, and the median particle size ranged from 0.000811 to 0.0013976 inches. Other bed material samples were collected at streamflow-gaging stations on the

  13. Changing abundance of Hexagenia mayfly nymphs in western Lake Erie of the Laurentian Great Lakes: Impediments to assessment of lake recovery?

    USGS Publications Warehouse

    Schloesser, D.W.; Nalepa, T.F.

    2001-01-01

    After an absence of 40 years, mayfly nymphs of the genus Hexagenia were found in sediments of western Lake Erie of the Laurentian Great Lakes in 1993 and, by 1997, were abundant enough to meet a mayfly-density management goal (ca. 350 nymphs m—2) based on pollution-abatement programs. We sampled nymphs in western Lake Erie and Lake St. Clair, located upstream of western Lake Erie, to determine the importance of seasonal abundance and life-history characteristics of nymphs (e.g., emergence and recruitment) on density estimates relative to the mayfly-density management goal. Two types of density patterns were observed: (1) densities were relatively high in spring and gradually decreased through late summer (observed in Lake Erie and Lake St. Clair in 1997 and Lake St. Clair in 1999) and (2) densities were relatively high in spring, gradually decreased to mid summer, abruptly decreased in mid summer, and then increased between summer and late fall (Lake Erie and Lake St. Clair in 1998 and Lake Erie in 1999). Length-frequency distributions of nymphs and observations of adults indicate that the primary cause for the two density patterns was attributed to failed (first pattern) and successful (second pattern) reproduction and emergence of nymphs into adults in mid summer. Gradual declines in densities were attributed to mortality of nymphs. Our results indicate that caution should be used when evaluating progress of pollution-abatement programs based on mayfly densities because recruitment success is variable both between and within years. Additionally, the interpretation of progress toward management goals, relative to the restoration of Hexagenia populations in the Great Lakes and possibly other water bodies throughout the world, is influenced by the number of years in which consequtive collections are made.

  14. Halogen and trace element geochemistry in Mid-Ocean Ridge basalts from the Australian-Antarctic Ridge (AAR)

    NASA Astrophysics Data System (ADS)

    Yang, Y. S.; Seo, J. H.; Park, S. H.; Kim, T.

    2015-12-01

    Australian-Antarctic Ridge (AAR) is an extension of easternmost SE Indian Mid-Ocean Ridge (MOR).We collected volcanic glasses from the "in-axis" of the KR1 and KR2 MOR, and the overlapping zones of the KR1 MOR and the nearby seamounts ("KR1 mixing"). We determined trace and halogen elements in the glasses. Halogen concentrations and its ratios in the glasses are important to understand the mantle metasomatism and volatile recycling. 52 of the collected glasses are "primitive" (higher than 6 wt% MgO), while 3 of them have rather "evolved" composition (MgO wt% of 1.72, 2.95 and 4.15). K2O concentrations and Th/Sc ratios in the glasses show a negative correlation with its MgO concentration. Incompatible element ratios such as La/Sm are rather immobile during a magma differentiation so the ratios are important to understand mantle composition (Hofmann et al. 2003). La/Sm ratios in the glasses are 0.95 ~ 3.28 suggesting that the AAR basalts can be classified into T-MORB and E-MORB (Schilling et al., 1983). La/Sm ratios are well-correlated with incompatible elements such as U, Ba, Nb, and negatively correlated with compatible elements such as Sc, Eu2+, Mg. The AAR glasses contain detectable halogen elements. The "KR1 mixing" glasses in halogen elements are more abundant than "in-axis" the glasses. Cl is the least variable element compared to the other halogens such as Br and I in the AAR. The "KR1 mixing" glasses have the largest variations of Br/Cl ratios compared to the "in-axis" glasses. The Cl/Br and Th/Sc ratios in the "in-axis" glasses and in the "KR1 mixing" glasses show positive and negative correlations, respectively. The Br-rich glasses in the "KR1 mixing" zone might be explained by a recycled Br-rich oceanic slab of paleo-subduction or by a hydrothermal alteration in the AAR. I composition in the glasses does not show a correlation other trace elements. The K/Cl and K/Ti ratios in the AAR glasses are similar to the basalts from the Galapagos Spreading Center

  15. The Tribolium castaneum Ortholog of Sex combs reduced Controls Dorsal Ridge Development

    PubMed Central

    Shippy, Teresa D.; Rogers, Carmelle D.; Beeman, Richard W.; Brown, Susan J.; Denell, Robin E.

    2006-01-01

    In insects, the boundary between the embryonic head and thorax is formed by the dorsal ridge, a fused structure composed of portions of the maxillary and labial segments. However, the mechanisms that promote development of this unusual structure remain a mystery. In Drosophila, mutations in the Hox genes Sex combs reduced and Deformed have been reported to cause abnormal dorsal ridge formation, but the significance of these abnormalities is not clear. We have identified three mutant allele classes of Cephalothorax, the Tribolium castaneum (red flour beetle) ortholog of Sex combs reduced, each of which has a different effect on dorsal ridge development. By using Engrailed expression to monitor dorsal ridge development in these mutants, we demonstrate that Cephalothorax promotes the fusion and subsequent dorsolateral extension of the maxillary and labial Engrailed stripes (posterior compartments) during dorsal ridge formation. Molecular and genetic analysis of these alleles indicates that the N terminus of Cephalothorax is important for the fusion step, but is dispensable for Engrailed stripe extension. Thus, we find that specific regions of Cephalothorax are required for discrete steps in dorsal ridge formation. PMID:16849608

  16. 33 CFR 162.220 - Hoover Dam, Lake Mead, and Lake Mohave (Colorado River), Ariz.-Nev.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 33 Navigation and Navigable Waters 2 2011-07-01 2011-07-01 false Hoover Dam, Lake Mead, and Lake... REGULATIONS § 162.220 Hoover Dam, Lake Mead, and Lake Mohave (Colorado River), Ariz.-Nev. (a) Lake Mead and... the axis of Hoover Dam and that portion of Lake Mohave (Colorado River) extending 4,500 feet...

  17. 33 CFR 162.220 - Hoover Dam, Lake Mead, and Lake Mohave (Colorado River), Ariz.-Nev.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 33 Navigation and Navigable Waters 2 2012-07-01 2012-07-01 false Hoover Dam, Lake Mead, and Lake... REGULATIONS § 162.220 Hoover Dam, Lake Mead, and Lake Mohave (Colorado River), Ariz.-Nev. (a) Lake Mead and... the axis of Hoover Dam and that portion of Lake Mohave (Colorado River) extending 4,500 feet...

  18. 33 CFR 162.220 - Hoover Dam, Lake Mead, and Lake Mohave (Colorado River), Ariz.-Nev.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 33 Navigation and Navigable Waters 2 2013-07-01 2013-07-01 false Hoover Dam, Lake Mead, and Lake... REGULATIONS § 162.220 Hoover Dam, Lake Mead, and Lake Mohave (Colorado River), Ariz.-Nev. (a) Lake Mead and... the axis of Hoover Dam and that portion of Lake Mohave (Colorado River) extending 4,500 feet...

  19. 33 CFR 162.220 - Hoover Dam, Lake Mead, and Lake Mohave (Colorado River), Ariz.-Nev.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 33 Navigation and Navigable Waters 2 2014-07-01 2014-07-01 false Hoover Dam, Lake Mead, and Lake... REGULATIONS § 162.220 Hoover Dam, Lake Mead, and Lake Mohave (Colorado River), Ariz.-Nev. (a) Lake Mead and... the axis of Hoover Dam and that portion of Lake Mohave (Colorado River) extending 4,500 feet...

  20. Lake Characteristics Influencing Spawning Success of Muskellunge in Northern Wisconsin Lakes

    Treesearch

    Ashley J. Rust; James S. Diana; Terry L. Margenau; Clayton J. Edwards

    2002-01-01

    We determined the physical, chemical, biological, and land use characteristics that distinguish northern Wisconsin lakes with self-sustaining populations of muskellunge Esox masquinongy from lakes where stocking is required to maintain populations. Lakes that supported self-sustaining muskellunge populations were characterized by fewer shoreline...

  1. Evaluating COSMO's lake module (FLake) for an East-African lake using a comprehensive set of lake temperature profiles

    NASA Astrophysics Data System (ADS)

    Thiery, W.; Martynov, A.; Darchambeau, F.; Demuzere, M.; van Lipzig, N.

    2012-04-01

    The African great lakes are of utmost importance for the local economy (fishing), as well as being essential to the survival of the local people. During last decades, these lakes have been changing rapidly and their evolution is a major concern. Hence, it is important to correctly represent them in regional climate models for simulations over tropical Africa. However, so far lake models have been developed and tested primarily for boreal conditions. In this study, for the first time the freshwater lake model FLake is evaluated over East-Africa, more specifically over lake Kivu. Meteorological observations from January 2003 to December 2008 from an automatic weather station in Bukavu, DRC, are used to drive the standalone version of FLake. For the evaluation, a unique dataset is used which contains over 200 temperature profiles recorded since 2002. Results show that FLake in its default configuration is very successful at reproducing both the timing and magnitude of the seasonal cycle at 5 m depth. Flake captures that this seasonality is regulated by the water vapour pressure, which constrains evaporation except during summer (JJA). A positive bias of ~1 K is attributed to the driving data, which are collected in the city and are therefore expected to mirror higher temperatures and lower wind speeds compared to the lake surface. The evaluation also showed that driving FLake with Era-Interim from the nearest pixel does only slightly deteriorate the model performance. Using forcing fields from the Canadian Regional Climate Model, version 5 (CRCM5) simulation output gives similar performance as Era-Interim. Furthermore, a drawback of FLake is that it does not account for salinity and its effect upon lake stratification, and therefore requires artificial initial conditions for both lake depth and bottom temperature in order to reproduce the correct mixing regime in lake Kivu. Further research will therefore aim at improving FLake's representation of tropical lakes.

  2. Ridge Segmentation, Tectonic Evolution and Rheology of Slow-Spreading Oceanic Crust

    DTIC Science & Technology

    1996-09-01

    important source of motivation, information, and geological field trips (remember Canarias , HeMn3’?). Dave Aubrey guided me on my first steps in Woods Hole... volcanic Ruppel, C., and P. Shaw. An elastic plate thickness map of the Mid- segmentation of the Mid-Atlantic Ridge: Kane to Atlantis Fracture Atlantic Ridge...76, 156, 1995. Smith, D. K., J. R. Cann, M. E. Dougherty, J. Lin, J. Keeton, E. McAllister, C. J. MacLeod and S. Spencer, Mid-Atlantic ridge volcanism

  3. Seasonal thermal ecology of adult walleye (Sander vitreus) in Lake Huron and Lake Erie.

    PubMed

    Peat, Tyler B; Hayden, Todd A; Gutowsky, Lee F G; Vandergoot, Christopher S; Fielder, David G; Madenjian, Charles P; Murchie, Karen J; Dettmers, John M; Krueger, Charles C; Cooke, Steven J

    2015-10-01

    The purpose of this study was to characterize thermal patterns and generate occupancy models for adult walleye from lakes Erie and Huron with internally implanted biologgers coupled with a telemetry study to assess the effects of sex, fish size, diel periods, and lake. Sex, size, and diel periods had no effect on thermal occupancy of adult walleye in either lake. Thermal occupancy differed between lakes and seasons. Walleye from Lake Erie generally experienced higher temperatures throughout the spring and summer months than did walleye in Lake Huron, due to limnological differences between the lakes. Tagged walleye that remained in Saginaw Bay, Lake Huron (i.e., adjacent to the release location), as opposed to those migrating to the main basin of Lake Huron, experienced higher temperatures, and thus accumulated more thermal units (the amount of temperature units amassed over time) throughout the year. Walleye that migrated toward the southern end of Lake Huron occupied higher temperatures than those that moved toward the north. Consequently, walleye that emigrated from Saginaw Bay experienced thermal environments that were more favorable for growth as they spent more time within their thermal optimas than those that remained in Saginaw Bay. Results presented in this paper provide information on the thermal experience of wild fish in a large lake, and could be used to refine sex- and lake-specific bioenergetics models of walleye in the Great Lakes to enable the testing of ecological hypotheses. Copyright © 2015 Elsevier Ltd. All rights reserved.

  4. Seasonal thermal ecology of adult walleye (Sander vitreus) in Lake Huron and Lake Erie

    USGS Publications Warehouse

    Peat, Tyler B; Hayden, Todd A.; Gutowsky, Lee F G; Vandergoot, Christopher S.; Fielder, David G.; Madenjian, Charles P.; Murchie, Karen J; Dettmers, John M.; Krueger, Charles C.; Cooke, Steven J.

    2015-01-01

    The purpose of this study was to characterize thermal patterns and generate occupancy models for adult walleye from lakes Erie and Huron with internally implanted biologgers coupled with a telemetry study to assess the effects of sex, fish size, diel periods, and lake. Sex, size, and diel periods had no effect on thermal occupancy of adult walleye in either lake. Thermal occupancy differed between lakes and seasons. Walleye from Lake Erie generally experienced higher temperatures throughout the spring and summer months than did walleye in Lake Huron, due to limnological differences between the lakes. Tagged walleye that remained in Saginaw Bay, Lake Huron (i.e., adjacent to the release location), as opposed to those migrating to the main basin of Lake Huron, experienced higher temperatures, and thus accumulated more thermal units (the amount of temperature units amassed over time) throughout the year. Walleye that migrated toward the southern end of Lake Huron occupied higher temperatures than those that moved toward the north. Consequently, walleye that emigrated from Saginaw Bay experienced thermal environments that were more favorable for growth as they spent more time within their thermal optimas than those that remained in Saginaw Bay. Results presented in this paper provide information on the thermal experience of wild fish in a large lake, and could be used to refine sex- and lake-specific bioenergetics models of walleye in the Great Lakes to enable the testing of ecological hypotheses.

  5. An enhanced structure tensor method for sea ice ridge detection from GF-3 SAR imagery

    NASA Astrophysics Data System (ADS)

    Zhu, T.; Li, F.; Zhang, Y.; Zhang, S.; Spreen, G.; Dierking, W.; Heygster, G.

    2017-12-01

    In SAR imagery, ridges or leads are shown as the curvilinear features. The proposed ridge detection method is facilitated by their curvilinear shapes. The bright curvilinear features are recognized as the ridges while the dark curvilinear features are classified as the leads. In dual-polarization HH or HV channel of C-band SAR imagery, the bright curvilinear feature may be false alarm because the frost flowers of young leads may show as bright pixels associated with changes in the surface salinity under calm surface conditions. Wind roughened leads also trigger the backscatter increasing that can be misclassified as ridges [1]. Thus the width limitation is considered in this proposed structure tensor method [2], since only shape feature based method is not enough for detecting ridges. The ridge detection algorithm is based on the hypothesis that the bright pixels are ridges with curvilinear shapes and the ridge width is less 30 meters. Benefited from GF-3 with high spatial resolution of 3 meters, we provide an enhanced structure tensor method for detecting the significant ridge. The preprocessing procedures including the calibration and incidence angle normalization are also investigated. The bright pixels will have strong response to the bandpass filtering. The ridge training samples are delineated from the SAR imagery in the Log-Gabor filters to construct structure tensor. From the tensor, the dominant orientation of the pixel representing the ridge is determined by the dominant eigenvector. For the post-processing of structure tensor, the elongated kernel is desired to enhance the ridge curvilinear shape. Since ridge presents along a certain direction, the ratio of the dominant eigenvector will be used to measure the intensity of local anisotropy. The convolution filter has been utilized in the constructed structure tensor is used to model spatial contextual information. Ridge detection results from GF-3 show the proposed method performs better compared to the

  6. Hydrology of Indiana lakes

    USGS Publications Warehouse

    Perrey, Joseph Irving; Corbett, Don Melvin

    1956-01-01

    The stabilization of lake levels often requires the construction of outlet control structures. A detailed study of past lake-level elevations and other hydologic date is necessary to establish a level that can be maintained and to determine the means necessary for maintaining the established level. Detailed lake-level records for 28 lakes are included in the report, and records for over 100 other lakes data are available in the U.S. Geological Survey Office, Indianapolis, Ind. Evaporation data from the four Class A evaporation station of the U. S. Weather Bureau have been compiled in this report. A table showing the established legal lake level and related data is included.

  7. First evidence of successful natural reproduction by planted lake trout in Lake Huron

    USGS Publications Warehouse

    Nester, Robert T.; Poe, Thomas P.

    1984-01-01

    Twenty-two lake trout (Salvelinus namaycush) swim-up fry, 24-27 mm long, were captured with emergent fry traps and a tow net in northwestern Lake Huron on a small nearshore reef off Alpena, Michigan, between May 10 and June 1, 1982. These catches represent the first evidence of successful production of swim-up fry by planted, hatchery-reared lake trout in Lake Huron since the lake trout rehabilitation program began in 1973.

  8. Estimation of lake water - groundwater interactions in meromictic mining lakes by modelling isotope signatures of lake water.

    PubMed

    Seebach, Anne; Dietz, Severine; Lessmann, Dieter; Knoeller, Kay

    2008-03-01

    A method is presented to assess lake water-groundwater interactions by modelling isotope signatures of lake water using meteorological parameters and field data. The modelling of delta(18)O and deltaD variations offers information about the groundwater influx into a meromictic Lusatian mining lake. Therefore, a water balance model is combined with an isotope water balance model to estimate analogies between simulated and measured isotope signatures within the lake water body. The model is operated with different evaporation rates to predict delta(18)O and deltaD values in a lake that is only controlled by weather conditions with neither groundwater inflow nor outflow. Comparisons between modelled and measured isotope values show whether the lake is fed by the groundwater or not. Furthermore, our investigations show that an adaptation of the Craig and Gordon model [H. Craig, L.I. Gordon. Deuterium and oxygen-18 variations in the ocean and the marine atmosphere. In Stable Isotopes in Oceanographic Studies and Paleotemperature, Spoleto, E. Tongiorgi (Ed.), pp. 9-130, Consiglio Nazionale delle Ricerche, Laboratorio di Geologia Nucleare, Pisa (1965).] to specific conditions in temperate regions seems necessary.

  9. Surface morphology of caldera-forming eruption deposits revealed by lidar mapping of Crater Lake National Park, Oregon- Implications for emplacement and surface modification

    USGS Publications Warehouse

    Robinson, Joel E.; Bacon, Charles R.; Major, Jon J.; Wright, Heather M.; Vallance, James W.

    2017-01-01

    Large explosive eruptions of silicic magma can produce widespread pumice fall, extensive ignimbrite sheets, and collapse calderas. The surfaces of voluminous ignimbrites are rarely preserved or documented because most terrestrial examples are heavily vegetated, or severely modified by post-depositional processes. Much research addresses the internal sedimentary characteristics, flow processes, and depositional mechanisms of ignimbrites, however, surface features of ignimbrites are less well documented and understood, except for comparatively small-volume deposits of historical eruptions. The ~7,700 calendar year B.P. climactic eruption of Mount Mazama, USA vented ~50 km3 of magma, deposited first as rhyodacite pumice fall and then as a zoned rhyodacite-to-andesite ignimbrite as Crater Lake caldera collapsed. Lidar collected during summer 2010 reveals the remarkably well-preserved surface of the Mazama ignimbrite and related deposits surrounding Crater Lake caldera in unprecedented detail despite forest cover. The ±1 m lateral and ±4 cm vertical resolution lidar allows surface morphologies to be classified. Surface morphologies are created by internal depositional processes and can point to the processes at work when pyroclastic flows come to rest. We describe nine surface features including furrow-ridge sets and wedge-shaped mounds in pumice fall eroded by high-energy pyroclastic surges, flow- parallel ridges that record the passage of multiple pyroclastic flows, perched benches of marginal deposits stranded by more-mobile pyroclastic-flow cores, hummocks of dense clasts interpreted as lag deposit, transverse ridges that mark the compression and imbrication of flows as they came to rest, scarps indicating ignimbrite remobilization, fields of pit craters caused by phreatic explosions, fractures and cracks caused by extensional processes resulting from ignimbrite volume loss, and stream channels eroded in the newly formed surface. The nine morphologies presented

  10. Surface morphology of caldera-forming eruption deposits revealed by lidar mapping of Crater Lake National Park, Oregon - Implications for deposition and surface modification

    NASA Astrophysics Data System (ADS)

    Robinson, Joel E.; Bacon, Charles R.; Major, Jon J.; Wright, Heather M.; Vallance, James W.

    2017-08-01

    Large explosive eruptions of silicic magma can produce widespread pumice fall, extensive ignimbrite sheets, and collapse calderas. The surfaces of voluminous ignimbrites are rarely preserved or documented because most terrestrial examples are heavily vegetated, or severely modified by post-depositional processes. Much research addresses the internal sedimentary characteristics, flow processes, and depositional mechanisms of ignimbrites, however, surface features of ignimbrites are less well documented and understood, except for comparatively small-volume deposits of historical eruptions. The 7700 calendar year B.P. climactic eruption of Mount Manama, USA, vented 50 km3 of magma, deposited first as rhyodacite pumice fall and then as a zoned rhyodacite-to-andesite ignimbrite as Crater Lake caldera collapsed. Lidar collected during summer 2010 reveals the remarkably well-preserved surface of the Manama ignimbrite and related deposits surrounding Crater Lake caldera in unprecedented detail despite forest cover. The ± 1 m lateral and ± 4 cm vertical resolution lidar allows surface morphologies to be classified. Surface morphologies are created by internal depositional processes and can point to the processes at work when pyroclastic flows come to rest. We describe nine surface features including furrow-ridge sets and wedge-shaped mounds in pumice fall eroded by high-energy pyroclastic surges, flow-parallel ridges that record the passage of multiple pyroclastic flows, perched benches of marginal deposits stranded by more-mobile pyroclastic-flow cores, hummocks of dense clasts interpreted as lag deposit, transverse ridges that mark the compression and imbrication of flows as they came to rest, scarps indicating ignimbrite remobilization, fields of closely spaced pits caused by phreatic explosions, fractures and cracks due to extensional processes resulting from ignimbrite volume loss, and stream channels eroded in the newly formed surface. The nine morphologies

  11. Maturation of large scale mass-wasting along the Hawaiian Ridge

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Torresan, M.E.; Clague, D.A.; Moore, J.G.

    1990-06-01

    Extensive GLORIA side-scan sonar mapping of the Hawaiian Ridge from Hawaii to St. Rogatien Bank shows that massive slumps and blocky debris avalanches are the major degradational processes that affect the island and ridge areas. About 30 failures have been imaged in the region surveyed; they range in area from 250 to > 6,000 km{sup 2} and in volume from 500 to > 5,000 km{sup 3}. Four are rotational slumps, and the rest are blocky debris avalanches. Such deposits cover 125,000 km{sup 2} of the Hawaiian Ridge and adjacent seafloor. The slumps are wide (up to 110 km), short (30-35more » km), thick (about 10 km), and slow moving. They are broken into comparatively few major rotational blocks that have not moved far and are characterized by steep toes and transverse ridges. Back rotation of the blocks has elevated their seaward edges, producing transverse ridges and perched basins filled with 5 to > 35 m of sediment. Compared to the slumps, the debris avalanches are lobate, long (up to 230 km), thin (0.5-2 km), and fast-moving. These deposits cross the Hawaiian Trough and run upslope onto the Hawaiian Arch (up to 550 m in elevation over a distance of 140 km). These failures commonly have amphitheaters and subaerial canyons at their heads. Their distal ends are hummocky, and blocky debris litters the seafloor adjacent to the ridge. As one proceeds west from Hawaii to St. Rogatien Bank, the GLORIA sonographs and seismic reflection profiles show a progression from youthful to mature failures and from active to about 12 Ma volcanoes. The Alika and Hilina slide complexes are examples of youthful failures on active volcanoes. Slumping in the Hilina slide is ongoing (7.2 magnitude earthquake in 1975). Little to no sediment covers the blocks and hummocky terrane of the Alika (about 100 ka), whereas the older deposits along the western part of the ridge are covered by up to 30 m of transparent sediment.« less

  12. 75 FR 13232 - Safety Zone; Lake Mead Intake Construction, Lake Mead, Boulder City, NV

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-03-19

    ...-AA00 Safety Zone; Lake Mead Intake Construction, Lake Mead, Boulder City, NV AGENCY: Coast Guard, DHS... waters of Lake Mead in support of the construction project for Lake Mead's Intake 3. This safety zone is... for the placement of an Intake Pipe from Lake Mead throughout 2010. This safety zone is necessary to...

  13. 78 FR 17869 - Safety Zone; Desert Storm Shootout; Lake Havasu, Lake Havasu City, AZ

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-03-25

    ...-AA00 Safety Zone; Desert Storm Shootout; Lake Havasu, Lake Havasu City, AZ AGENCY: Coast Guard, DHS... navigable waters of the Colorado River in Lake Havasu, Lake Havasu City, Arizona in support of the Desert... Coast Guard to establish safety zones (33 U.S.C 1221 et seq.). Lake Racer LLC is sponsoring the Desert...

  14. Bioturbation enhances the aerobic respiration of lake sediments in warming lakes.

    PubMed

    Baranov, Viktor; Lewandowski, Jörg; Krause, Stefan

    2016-08-01

    While lakes occupy less than 2% of the total surface of the Earth, they play a substantial role in global biogeochemical cycles. For instance, shallow lakes are important sites of carbon metabolism. Aerobic respiration is one of the important drivers of the carbon metabolism in lakes. In this context, bioturbation impacts of benthic animals (biological reworking of sediment matrix and ventilation of the sediment) on sediment aerobic respiration have previously been underestimated. Biological activity is likely to change over the course of a year due to seasonal changes of water temperatures. This study uses microcosm experiments to investigate how the impact of bioturbation (by Diptera, Chironomidae larvae) on lake sediment respiration changes when temperatures increase. While at 5°C, respiration in sediments with and without chironomids did not differ, at 30°C sediment respiration in microcosms with 2000 chironomids per m(2) was 4.9 times higher than in uninhabited sediments. Our results indicate that lake water temperature increases could significantly enhance lake sediment respiration, which allows us to better understand seasonal changes in lake respiration and carbon metabolism as well as the potential impacts of global warming. © 2016 The Authors.

  15. Bioturbation enhances the aerobic respiration of lake sediments in warming lakes

    PubMed Central

    Krause, Stefan

    2016-01-01

    While lakes occupy less than 2% of the total surface of the Earth, they play a substantial role in global biogeochemical cycles. For instance, shallow lakes are important sites of carbon metabolism. Aerobic respiration is one of the important drivers of the carbon metabolism in lakes. In this context, bioturbation impacts of benthic animals (biological reworking of sediment matrix and ventilation of the sediment) on sediment aerobic respiration have previously been underestimated. Biological activity is likely to change over the course of a year due to seasonal changes of water temperatures. This study uses microcosm experiments to investigate how the impact of bioturbation (by Diptera, Chironomidae larvae) on lake sediment respiration changes when temperatures increase. While at 5°C, respiration in sediments with and without chironomids did not differ, at 30°C sediment respiration in microcosms with 2000 chironomids per m2 was 4.9 times higher than in uninhabited sediments. Our results indicate that lake water temperature increases could significantly enhance lake sediment respiration, which allows us to better understand seasonal changes in lake respiration and carbon metabolism as well as the potential impacts of global warming. PMID:27484649

  16. Lake Sturgeon, Acipenser fulvescens, movements in Rainy Lake, Minnesota and Ontario

    USGS Publications Warehouse

    Adams, W.E.; Kallemeyn, L.W.; Willis, D.W.

    2006-01-01

    Rainy Lake, Minnesota-Ontario, contains a native population of Lake Sturgeon (Acipenser fulvescens) that has gone largely unstudied. The objective of this descriptive study was to summarize generalized Lake Sturgeon movement patterns through the use of biotelemetry. Telemetry data reinforced the high utilization of the Squirrel Falls geographic location by Lake Sturgeon, with 37% of the re-locations occurring in that area. Other spring aggregations occurred in areas associated with Kettle Falls, the Pipestone River, and the Rat River, which could indicate spawning activity. Movement of Lake Sturgeon between the Seine River and the South Arm of Rainy Lake indicates the likelihood of one integrated population on the east end of the South Arm. The lack of re-locations in the Seine River during the months of September and October may have been due to Lake Sturgeon moving into deeper water areas of the Seine River and out of the range of radio telemetry gear or simply moving back into the South Arm. Due to the movements between Minnesota and Ontario, coordination of management efforts among provincial, state, and federal agencies will be important.

  17. 77 FR 41399 - Combined Notice of Filings #2

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-07-13

    ..., LLC, Butler Ridge Wind Energy Center, Crystal Lake Wind, LLC, Crystal Lake Wind II, LLC, Crystal Lake.... Eastern time on the specified comment date. Protests may be considered, but intervention is necessary to...

  18. Hydrodynamic role of longitudinal dorsal ridges in a leatherback turtle swimming

    PubMed Central

    Bang, Kyeongtae; Kim, Jooha; Lee, Sang-Im; Choi, Haecheon

    2016-01-01

    Leatherback sea turtles (Dermochelys coriacea) are known to have a superior diving ability and be highly adapted to pelagic swimming. They have five longitudinal ridges on their carapace. Although it was conjectured that these ridges might be an adaptation for flow control, no rigorous study has been performed to understand their hydrodynamic roles. Here we show that these ridges are slightly misaligned to the streamlines around the body to generate streamwise vortices, and suppress or delay flow separation on the carapace, resulting in enhanced hydrodynamic performances during different modes of swimming. Our results suggest that shapes of some morphological features of living creatures, like the longitudinal ridges of the leatherback turtles, need not be streamlined for excellent hydro- or aerodynamic performances, contrary to our common physical intuition. PMID:27694826

  19. Data Sharing Report Characterization of Isotope Row Facilities Oak Ridge National Laboratory Oak Ridge TN

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Weaver, Phyllis C.

    The U.S. Department of Energy (DOE) Oak Ridge Office of Environmental Management (EM-OR) requested that Oak Ridge Associated Universities (ORAU), working under the Oak Ridge Institute for Science and Education (ORISE) contract, provide technical and independent waste management planning support using funds provided by the American Recovery and Reinvestment Act (ARRA). Specifically, DOE EM-OR requested ORAU to plan and implement a survey approach, focused on characterizing the Isotope Row Facilities located at the Oak Ridge National Laboratory (ORNL) for future determination of an appropriate disposition pathway for building debris and systems, should the buildings be demolished. The characterization effort wasmore » designed to identify and quantify radiological and chemical contamination associated with building structures and process systems. The Isotope Row Facilities discussed in this report include Bldgs. 3030, 3031, 3032, 3033, 3033A, 3034, 3036, 3093, and 3118, and are located in the northeast quadrant of the main ORNL campus area, between Hillside and Central Avenues. Construction of the isotope production facilities was initiated in the late 1940s, with the exception of Bldgs. 3033A and 3118, which were enclosed in the early 1960s. The Isotope Row facilities were intended for the purpose of light industrial use for the processing, assemblage, and storage of radionuclides used for a variety of applications (ORNL 1952 and ORAU 2013). The Isotope Row Facilities provided laboratory and support services as part of the Isotopes Production and Distribution Program until 1989 when DOE mandated their shutdown (ORNL 1990). These facilities performed diverse research and developmental experiments in support of isotopes production. As a result of the many years of operations, various projects, and final cessation of operations, production was followed by inclusion into the surveillance and maintenance (S&M) project for eventual decontamination and decommissioning (D

  20. High-resolution record of the Laschamp geomagnetic excursion at the Blake-Bahama Outer Ridge

    NASA Astrophysics Data System (ADS)

    Bourne, Mark D.; Mac Niocaill, Conall; Thomas, Alex L.; Henderson, Gideon M.

    2013-12-01

    Geomagnetic excursions are brief deviations of the geomagnetic field from behaviour expected during `normal secular' variation. The Laschamp excursion at ˜41 ka was one such deviation. Previously published records suggest rapid changes in field direction and a concurrent substantial decrease in field intensity associated with this excursion. Accurate dating of excursions, and determination of their durations from multiple locations, is vital to our understanding of global field behaviour during these deviations. We present here high-resolution palaeomagnetic records of the Laschamp excursion obtained from two Ocean Drilling Program (ODP) Sites, 1061 and 1062 on the Blake-Bahama Outer Ridge (ODP Leg 172). High sedimentation rates (˜30-40 cm kyr-1) at these locations allow determination of transitional field behaviour during the excursion. Palaeomagnetic measurements of discrete samples from four cores reveal a single excursional feature, across an interval of 30 cm, associated with a broader palaeointensity low. We determine the age and duration of the Laschamp excursion using a stratigraphy linked to the δ18O record from the Greenland ice cores. This chronology dates the Laschamp excursion at the Blake Ridge to 41.3 ka. The excursion is characterized by rapid transitions (less than 200 yr) between stable normal polarity and a partially reversed polarity state. The palaeointensity record is in good agreement between the two sites, revealing two prominent minima. The first minimum is associated with the Laschamp excursion at 41 ka and the second corresponds to the Mono Lake excursion at ˜35.5 ka. We determine that the directional excursion during the Laschamp at this location was no longer than ˜400 yr, occurring within a palaeointensity minimum that lasted 2000 yr. The Laschamp excursion at this location is much shorter in duration than the Blake and Iceland Basin excursions.

  1. Mantle Sources Beneath the SW Indian Ridge - Remelting the African Superplume

    NASA Astrophysics Data System (ADS)

    Dick, H. J. B.; Zhou, H.

    2012-04-01

    The SW Indian Ridge runs some 7700 km from the Bouvet to the Rodgriguez Triple Junction, crossing over or near two postulated mantle plumes. The latter are associated with large oceanic rises where the ridge axis shoals dramatically in the vicinity of the mantle hotspot. The Marion Rise, extends 3100 km from the Andrew Bain FZ to near the Rodriguez TJ, with an along axis rise of 5600-m to it crest north of Marion Island. The rise has thin crust inferred on the basis of abundant exposures of mantle peridotites along its length. We suggest that this is the result of its sub-axial mantle source, which is a depleted residue originally emplaced by the African Superplume into the asthenosphere beneath southern Africa during the Karoo volcanic event ~185 Ma. Based on shallow mantle anisotropy, plate reconstructions, and hotspot traces, it now forms the mantle substrate for the SW Indian Ridge due to the breakup of Gondwanaland. The Marion Rise is associated with Marion Island, the present location of the Marion Hotspot, some 256 km south of the modern ridge. This plume is a vestigial remnant of the African Superplume now imbedded in and centered on asthenospheric mantle derived from the Karoo event. Based on the numerous large offset fracture zones, which would dam sub-axial asthenospheric flow along the ridge, the low postulated flux of the Marion plume, its off-axis position, and the thin crust along the ridge it is clear that the present day plume does not support the Marion Rise. Instead, this must be supported isostatically by the underlying mantle residue of the Karoo event. The Bouvet Rise is much shorter than the Marion Rise, extending ~664 km from the Conrad FZ on the American-Antarctic Ridge to the Shaka FZ on the SW Indian Ridge. It has ~3000-m of axial relief, peaking at Speiss Smt at Speiss Ridge: the last spreading segment of the SW Indian Ridge adjacent to the Bouvet TJ. Unlike the Marion plume, Bouvet is ridge-centered, and much of its rise is likely

  2. Geospatializing The Klang Gate Quartz Ridge in Malaysia: A Technological Perspective

    NASA Astrophysics Data System (ADS)

    Azahari Razak, Khamarrul; Mohamad, Zakaria; Zaki Ibrahim, Mohd; Azad Rosle, Qalam; Hattanajmie Abd Wahab, Mohd; Abu Bakar, Rabieahtul; Mohd Akib, Wan Abdul Aziz Wan

    2015-04-01

    Establishment of inventories on geological heritage, or geoheritage resources is a step forward for a comprehensive geoheritage management leading to a better conservation at national and global levels. Compiling and updating inventory of geoheritage is a tedious process and even so in a tropical environment. Malaysia has a tremendous list of geodiversity and generating its national database is a multi-institutional effort and worthwhile investment. However, producing accurate and reliable characteristics of such landform and spectacular geological features remained elusive. The advanced and modern mapping techniques have revolutionized the mapping, monitoring and modelling of the earth surface processes and landforms. Yet the methods for quantification of geodiversity physical features are not fully utilized in Malaysia for a better understanding its processes and activity. This study provides a better insight into the use of advanced active remote sensing technology for characterizing the forested Quartz Ridge in Malaysia. We have developed the novel method and tested in the Klang Gates Quartz Ridge, Selangor. The granitic country rock made up by quartz mineral is known as the longest quartz ridge in Malaysia and characterized by rugged topography, steep slopes, densely vegetated terrain and also rich-biodiversity area. This study presents an integrated field methodological framework and processing scheme by taking into account the climatic, topographic, geologic, and anthropogenic challenges in an equatorial region. Advanced terrestrial laser scanning system was used to accurately capture, map and model the ridge carried out within a relatively stringent time period. The high frequency Global Navigation Satellite System and modern Total Station coupled with the optical satellite and radar imageries and also advanced spatial analysis were fully utilized in the field campaign and data assessment performed during the recent monsoon season. As a result, the mapping

  3. Morphology of sea ice pressure ridges in the northwestern Weddell Sea in winter

    NASA Astrophysics Data System (ADS)

    Tan, Bing; Li, Zhi-Jun; Lu, Peng; Haas, Christian; Nicolaus, Marcel

    2012-06-01

    To investigate the morphology and distribution of pressure ridges in the northwestern Weddell Sea, ice surface elevation profiles were measured by a helicopter-borne laser altimeter during Winter Weddell Outflow Study with the German R/V Polarstern in 2006. An optimal cutoff height of 0.62 m, derived from the best fits between the measured and theoretical ridge height and spacing distributions, was first used to separate pressure ridges from other sea ice surface undulations. It was found that the measured ridge height distribution was well modeled by a negative exponential function, and the ridge spacing distribution by a lognormal function. Next, based on the ridging intensity Ri (the ratio of mean ridge sail height to mean spacing), all profiles were clustered into three regimes by an improved k-means clustering algorithm: Ri ≤ 0.01, 0.01 < Ri ≤ 0.026, and Ri > 0.026 (denoted as C1, C2, and C3 respectively). Mean (and standard deviation) of sail height was 0.99 (±0.07) m in Regime C1, 1.12 (±0.06) m in C2, and 1.17 (±0.04) m in C3, respectively, while the mean spacings (and standard deviations) were 232 (±240) m, 54 (±20) m, and 31 (±5.6) m. These three ice regimes coincided closely with distinct sea ice regions identified in a satellite radar image, where C1 corresponded to the broken ice in the marginal ice zone and level ice formed in the Larsen Polynya, C2 corresponded to the deformed first- and second-year ice formed by dynamic action in the center of the study region, and C3 corresponded to heavily deformed ice in the outflowing branch of the Weddell Gyre. The results of our analysis showed that the relationship between the mean ridge height and frequency was well modeled by a logarithmic function with a correlation coefficient of 0.8, although such correlation was weaker when considering each regime individually. The measured ridge height and frequency were both greater than those reported by others for the Ross Sea. Compared with reported

  4. Stratigraphic framework and lake level history of Lake Kivu, East African Rift

    NASA Astrophysics Data System (ADS)

    Wood, Douglas A.; Scholz, Christopher A.

    2017-10-01

    Sediment cores and seismic reflection data acquired from the eastern basin of Lake Kivu, Rwanda reveal extensive limnologic variations due to changes in regional climate and basin structure. The eastern basin of the lake contains a sedimentary wedge which is > 1.5 km in thickness on its western side, and basal sediments are estimated to be at least 1.5 million years old. Sediments are likely to be thicker and older than this in the northern, Congolese basin of the lake. Above the ∼300 m iosbath only a thin layer of Holocene sediments are observed indication that this may have been the lake's high stand prior to that time. There are at least three erosional unconformities interpreted as desiccation or near-desiccation events which are estimated to have occurred at ∼475 ka, ∼100 ka, and ∼20 ka; the two most recent of these low stages likely developed during the African Megadrought and Last Glacial Maximum (LGM) periods. Following the LGM, the water levels rose to form a ∼100 m deep lake with its surface ∼370 m below the current lake level. The lake remained near that level for several thousand years and during this time the Virunga Volcanic Province expanded. At ∼12.2 ka a change to wetter climate conditions rapidly filled the lake to spill out of the Bukavu Bay basin southward toward Lake Tanganyika. Tephra sampled from the cores show that there have been at least 24 large local volcanic events since the early Holocene lake transgression.

  5. Hydrology of Crater, East and Davis Lakes, Oregon; with section on Chemistry of the Lakes

    USGS Publications Warehouse

    Phillips, Kenneth N.; Van Denburgh, A.S.

    1968-01-01

    Crater, East, and Davis Lakes are small bodies of fresh water that occupy topographically closed basins in Holocene volcanic terrane. Because the annual water supply exceeds annual evaporation, water must be lost by seepage from each lake. The seepage rates vary widely both in volume and in percentage of the total water supply. Crater Lake loses about 89 cfs (cubic feet per second), equivalent to about 72 percent of its average annual supply. East Lake loses about 2.3 cfs, or about 44 percent of its estimated supply. Davis Lake seepage varies greatly with lake level, but the average loss is about 150 cfs, more than 90 percent of its total supply. The destination of the seepage loss is not definitely known for any of the lakes. An approximate water budget was computed for stationary level for each lake, by using estimates 'by the writer to supplement the hydrologic data available. The three lake waters are dilute. Crater Lake contains about 80 ppm, (parts per million) of dissolved solids---mostly silica, sodium, and bicarbonate, and lesser amounts of calcium, sulfate, and chloride. Much of the dissolved-solids content of Crater Lake---especially the sulfate and chloride---may be related to fumarole and thermal-spring activity that presumably followed the collapse of Mount Mazama. Although Grater Lake loses an estimated 7,000 tons of its 1.5million-ton salt content each year by leakage, the chemical character of the lake did not change appreciably between 1912 and 1964. East Lake contains 200 ppm of dissolved solids, which includes major proportions of calcium, sodium, bicarbonate, and sulfate, but almost no chloride. The lake apparently receives much of its dissolved solids from subsurface thermal springs. Annual solute loss from East Lake by leakage is about 450 tons, or 3 percent of the lake's 15,000-ton estimated solute content. Davis Lake contains only 48 ppm of dissolved solids, much of which is silica and bicarbonate; chloride is almost completely absent

  6. 76 FR 2579 - Safety Zone; Lake Mead Intake Construction, Lake Mead, Boulder City, NV

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-01-14

    ...-AA00 Safety Zone; Lake Mead Intake Construction, Lake Mead, Boulder City, NV AGENCY: Coast Guard, DHS... waters of Lake Mead in support of the construction project for Lake Mead's Intake 3 during the first 6... blasting operations for the placement of a water intake pipe in Lake Mead during the first 6 months of 2011...

  7. Evaluation of methods to estimate lake herring spawner abundance in Lake Superior

    USGS Publications Warehouse

    Yule, D.L.; Stockwell, J.D.; Cholwek, G.A.; Evrard, L.M.; Schram, S.; Seider, M.; Symbal, M.

    2006-01-01

    Historically, commercial fishers harvested Lake Superior lake herring Coregonus artedi for their flesh, but recently operators have targeted lake herring for roe. Because no surveys have estimated spawning female abundance, direct estimates of fishing mortality are lacking. The primary objective of this study was to determine the feasibility of using acoustic techniques in combination with midwater trawling to estimate spawning female lake herring densities in a Lake Superior statistical grid (i.e., a 10′ latitude × 10′ longitude area over which annual commercial harvest statistics are compiled). Midwater trawling showed that mature female lake herring were largely pelagic during the night in late November, accounting for 94.5% of all fish caught exceeding 250 mm total length. When calculating acoustic estimates of mature female lake herring, we excluded backscattering from smaller pelagic fishes like immature lake herring and rainbow smelt Osmerus mordax by applying an empirically derived threshold of −35.6 dB. We estimated the average density of mature females in statistical grid 1409 at 13.3 fish/ha and the total number of spawning females at 227,600 (95% confidence interval = 172,500–282,700). Using information on mature female densities, size structure, and fecundity, we estimate that females deposited 3.027 billion (109) eggs in grid 1409 (95% confidence interval = 2.356–3.778 billion). The relative estimation error of the mature female density estimate derived using a geostatistical model—based approach was low (12.3%), suggesting that the employed method was robust. Fishing mortality rates of all mature females and their eggs were estimated at 2.3% and 3.8%, respectively. The techniques described for enumerating spawning female lake herring could be used to develop a more accurate stock–recruitment model for Lake Superior lake herring.

  8. Lake Chad, Chad, Africa

    NASA Image and Video Library

    1990-04-29

    Africa's Lake Chad where the borders of Chad, Niger, Nigeria and Cameroon merge (13.0N, 14.0E) has been undergoing change for the past 25 to 30 years when it was first noticed that the lake is drying up. Since then, astronauts have been photographing it on a regular basis to record the diminishing lake bed. This lake was once the aproximate size of Lake Erie but is now only about half that size and is still receeding.

  9. Water-quality and lake-stage data for Wisconsin lakes, water year 2014

    USGS Publications Warehouse

    Manteufel, S. Bridgett; Robertson, Dale M.

    2017-05-25

    IntroductionThe U.S. Geological Survey (USGS), in cooperation with local and other agencies, collects data at selected lakes throughout Wisconsin. These data, accumulated over many years, provide a database for developing an improved understanding of the water quality of lakes. To make these data available to interested parties outside the USGS, the data are published annually in this report series. The locations of water-quality and lake-stage stations in Wisconsin for water year 2014 are shown in figure 1. A water year is the 12-month period from October 1 through September 30. It is designated by the calendar year in which it ends. Thus, the periodOctober 1, 2013, through September 30, 2014, is called “water year 2014.”The purpose of this report is to provide information about the chemical and physical characteristics of Wisconsin lakes. Data that have been collected at specific lakes, and information to aid in the interpretation of those data, are included in this report. Data collected include measurements of in-lake water quality and lake stage. Time series of Secchi depths, surface total phosphorus, and chlorophyll a concentrations collected during nonfrozen periods are included for many lakes. Graphs of vertical profiles of temperature, dissolved oxygen, pH, and specific conductance are included for sites where these parameters were measured. Descriptive information for each lake includes the location of the lake, area of the lake’s watershed, period for which data are available, revisions to previously published records, and pertinent remarks. Additional data, such as streamflow and water quality in tributary and outlet streams of some of the lakes, are published online at http://nwis.waterdata.usgs.gov/wi/nwis.Water-resources data, including stage and discharge data at most streamflow-gaging stations, are available online. The Wisconsin Water Science Center’s home page is at https://www.usgs.gov/centers/wisconsin-water-science-center. Information

  10. The rise and fall of axial highs during ridge jumps

    NASA Astrophysics Data System (ADS)

    Shah, Anjana K.; Buck, W. Roger

    2006-08-01

    We simulate jumps of ocean spreading centers with axial high topography using elastoplastic thin plate flexure models. Processes considered include ridge abandonment, the breaking of a stressed plate on the ridge flank, and renewed spreading at the site of this break. We compare model results to topography at the East Pacific Rise between 15°25'N and 16°N, where there is strong evidence of a recent ridge jump. At an apparently abandoned ridge, gravity data do not suggest buoyant support of topography. Model deflections during cooling and melt solidification stages of ridge abandonment are of small vertical amplitude because of plate strengthening, resulting in the preservation of a "frozen" fossil high. The present-day high is bounded by slopes with up to a 40% grade, a scenario very difficult to achieve flexurally given generally accepted constraints on lithospheric strength. We model these slopes by assuming that the height at which magma is accreted increases rapidly after the ridge jumps. This increase is attributed to high overburden pressure on melt that resided in an initially deep magma chamber, followed by a rapid increase in temperature and melt supply to the region shortly after spreading began. The high is widest at the segment center, suggesting that magmatic activity began near the center of the segment, propagated south and then north. The mantle Bouguer anomaly exhibits a "bull's-eye" pattern centered at the widest part of the high, but the depth of the axis is nearly constant along the length of the segment. We reconcile these observations by assigning different cross-axis widths to a low-density zone within the crust.

  11. Helminths in an intensively stocked population of lake trout, Salvelinus namaycush, from Lake Huron

    USGS Publications Warehouse

    Muzzall, Patrick M.; Bowen, Charles A.

    2000-01-01

    Eighty stocked lake trout Salvelinus namaycush (Salmonidae), collected from 2 locations in Lake Huron in May 1995, were examined for parasites. The parasite fauna of this top predator in Lake Huron was characterized by only 6 helminth species. Echinorhynchus salmonis infected all lake trout with a mean intensity of 163.9. The intensity of this acanthocephalan species significantly increased with host length and weight. Eubothrium salvelini infected 78 lake trout with a maximum number of 81 scoleces counted. Diplostomum sp., Cyathocephalus truncatus, Capillaria salvelini, and Neoechinorhynchus sp. infrequently infected lake trout. The low parasite species richness in these lake trout is believed to be due to their large size at stocking and to the loss of historical enzootic host-parasite relationships that followed the absence of this fish species in Lake Huron for 26 yr.

  12. Glaciers, Glacial lakes and Glacial Lake Outburst Floods in the Koshi Basin

    NASA Astrophysics Data System (ADS)

    Shrestha, F.; Gao, X.; Khanal, N. R.; Maharjan, S. B.; Bajracharya, S. R.; Shrestha, R. B.; Lizong, W.; Mool, P. K.

    2016-12-01

    Glacier is a vital water resources for mountain communities. Recession in glacier area either increased the glacial lake size or develop a new lake. The consequences of these changes in lake has become one of the major issue in the management of GLOF risk. This paper presents the distribution of, and changes in, glaciers, glacial lakes in the Koshi basin and also looks at past GLOF events that have occurred in the basin and their distance of impact. Data on the number of glaciers and glacial lakes and their areas were generated for the years 1977, 1990, 2000, and 2010 using Landsat images. The study revealed that there were a total of 845 glaciers (Nepal side) and 2,168 glacial lakes (Nepal and China side) with a total area of 1,103 km2 and 127.608 km2 in 2010. The number of glacier increased by 15% (109) and area decreased by 26% (396 km2) over 33 years. In case of glacier lakes, the number and area increased from 1,160 to 2,168 and from 94.444 km2 to 127.608 km2 during 33 years with an overall growth rates of 86.9% and 35.1%. A large number of glacial lakes are small in size (≤ 0.1 km2). End moraine dammed lakes with area ≥ 0.1 km2 were selected to analyse the change characteristics of glacial lakes. The results show that there were 134 lakes ≥ 0.1 km2 in 2010; these lakes had a total area of 43.06 km2 in 1997, increased to 64.35 km2 in 2010. The distribution of lakes on the north side of the Himalayas (in China) was three times higher than on the south side of the Himalayas (in Nepal). Comparing the mean growth rate in area and length for the 33 years, the growth rate on the north side was found to be a little slower than that on the south side. This relationship did not hold true for length change in the different periods. The study identified 42 rapidly growing large lakes that are dangerous in terms of GLOF risk. In the past, 18 GLOF events have been reported. The downstream distance impacted by those events was up to 90 km. Among them, 13 GLOF events

  13. Lake Michigan lake trout PCB model forecast post audit (oral presentation)

    EPA Science Inventory

    Scenario forecasts for total PCBs in Lake Michigan (LM) lake trout were conducted using the linked LM2-Toxics and LM Food Chain models, supported by a suite of additional LM models. Efforts were conducted under the Lake Michigan Mass Balance Study and the post audit represents an...

  14. Simulating Lake-Groundwater Interactions During Decadal Climate Cycles: Accounting For Variable Lake Area In The Watershed

    NASA Astrophysics Data System (ADS)

    Virdi, M. L.; Lee, T. M.

    2009-12-01

    The volume and extent of a lake within the topo-bathymetry of a watershed can change substantially during wetter and drier climate cycles, altering the interaction of the lake with the groundwater flow system. Lake Starr and other seepage lakes in the permeable sandhills of central Florida are vulnerable to climate changes as they rely exclusively on rainfall and groundwater for inflows in a setting where annual rainfall and recharge vary widely. The groundwater inflow typically arrives from a small catchment area bordering the lake. The sinkhole origin of these lakes combined with groundwater pumping from underlying aquifers further complicate groundwater interactions. Understanding the lake-groundwater interactions and their effects on lake stage over multi-decadal climate cycles is needed to manage groundwater pumping and public expectation about future lake levels. The interdependence between climate, recharge, changing lake area and the groundwater catchment pose unique challenges to simulating lake-groundwater interactions. During the 10-year study period, Lake Starr stage fluctuated more than 13 feet and the lake surface area receded and expanded from 96 acres to 148 acres over drier and wetter years that included hurricanes, two El Nino events and a La Nina event. The recently developed Unsaturated Zone Flow (UZF1) and Lake (LAK7) packages for MODFLOW-2005 were used to simulate the changing lake sizes and the extent of the groundwater catchment contributing flow to the lake. The lake area was discretized to occupy the largest surface area at the highest observed stage and then allowed to change size. Lake cells convert to land cells and receive infiltration as receding lake area exposes the underlying unsaturated zone to rainfall and recharge. The unique model conceptualization also made it possible to capture the dynamic size of the groundwater catchment contributing to lake inflows, as the surface area and volume of the lake changed during the study

  15. Lake Granbury and Lake Whitney Assessment Initiative Final Scientific/Technical Report Summary

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Harris, B. L.; Roelke, Daniel; Brooks, Bryan

    A team of Texas AgriLife Research, Baylor University and University of Texas at Arlington researchers studied the biology and ecology of Prymnesium parvum (golden algae) in Texas lakes using a three-fold approach that involved system-wide monitoring, experimentation at the microcosm and mesocosm scales, and mathematical modeling. The following are conclusions, to date, regarding this organism's ecology and potential strategies for mitigation of blooms by this organism. In-lake monitoring revealed that golden algae are present throughout the year, even in lakes where blooms do not occur. Compilation of our field monitoring data with data collected by Texas Parks and Wildlife andmore » Brazos River Authority (a period spanning a decade) revealed that inflow and salinity variables affect bloom formations. Thresholds for algae populations vary per lake, likely due to adaptations to local conditions, and also to variations in lake-basin morphometry, especially the presence of coves that may serve as hydraulic storage zones for P. parvum populations. More specifically, our in-lake monitoring showed that the highly toxic bloom that occurred in Lake Granbury in the winter of 2006/2007 was eliminated by increased river inflow events. The bloom was flushed from the system. The lower salinities that resulted contributed to golden algae not blooming in the following years. However, flushing is not an absolute requirement for bloom termination. Laboratory experiments have shown that growth of golden algae can occur at salinities ~1-2 psu but only when temperatures are also low. This helps to explain why blooms are possible during winter months in Texas lakes. Our in-lake experiments in Lake Whitney and Lake Waco, as well as our laboratory experiments, revealed that cyanobacteria, or some other bacteria capable of producing algicides, were able to prevent golden algae from blooming. Identification of this organism is a high priority as it may be a key to managing golden algae

  16. Planktic foraminifer census data from Northwind Ridge Core 5, Arctic Ocean

    USGS Publications Warehouse

    Foley, Kevin M.; Poore, Richard Z.

    1991-01-01

    The U.S. Geological Survey recovered 9 piston cores from the Northwind Ridge in the Canada Basin of the Arctic Ocean from a cruise of the USCGC Polar Star during 1988. Preliminary analysis of the cores suggests sediments deposited on Northwind Ridge preserve a detailed record of glacial and interglacial cycles for the last few hundred-thousand to one million years. This report includes quantitative data on foraminifers and selected sediment size-fraction data in samples from Northwind Ridge core PI-88AR P5.

  17. Water balance of a lake with floodplain buffering: Lake Tana, Blue Nile Basin, Ethiopia

    NASA Astrophysics Data System (ADS)

    Dessie, Mekete; Verhoest, Niko E. C.; Pauwels, Valentijn R. N.; Adgo, Enyew; Deckers, Jozef; Poesen, Jean; Nyssen, Jan

    2015-03-01

    Lakes are very important components of the earth's hydrological cycle, providing a variety of services for humans and ecosystem functioning. For a sustainable use of lakes, a substantial body of knowledge on their water balance is vital. We present here a detailed daily water balance analysis for Lake Tana, the largest lake in Ethiopia and the source of the Blue Nile. Rainfall on the lake is determined by Thiessen polygon procedure, open water evaporation is estimated by the Penman-combination equation and observed inflows for the gauged catchments as well as outflow data at the two lake outlets are directly used. Runoff from ungauged catchments is estimated using a simple rainfall-runoff model and runoff coefficients. Hillslope catchments and floodplains are treated separately, which makes this study unique compared to previous water balance studies. Impact of the floodplain on the lake water balance is analyzed by conducting scenario-based studies. We found an average yearly abstraction of 420 × 106 m3 or 6% of river inflows to the lake by the floodplain in 2012 and 2013. Nearly 60% of the inflow to the lake is from the Gilgel Abay River. Simulated lake levels compare well with the observed lake levels (R2 = 0.95) and the water balance can be closed with a closure error of 82 mm/year (3.5% of the total lake inflow). This study demonstrates the importance of floodplains and their influence on the water balance of the lake and the need of incorporating the effects of floodplains and water abstraction for irrigation to improve predictions.

  18. Morphological variation of siscowet lake trout in Lake Superior

    USGS Publications Warehouse

    Bronte, C.R.; Moore, S.A.

    2007-01-01

    Historically, Lake Superior has contained many morphologically distinct forms of the lake trout Salvelinus namaycush that have occupied specific depths and locations and spawned at specific times of the year. Today, as was probably the case historically, the siscowet morphotype is the most abundant. Recent interest in harvesting siscowets to extract oil containing omega-3 fatty acids will require additional knowledge of the biology and stock structure of these lightly exploited populations. The objective of this study was to determine whether shape differences exist among siscowet populations across Lake Superior and whether these shape differences can be used to infer stock structure. Morphometric analysis (truss protocol) was used to differentiate among siscowets sampled from 23 locations in Lake Superior. We analyzed 31 distance measurements among 14 anatomical landmarks taken from digital images of fish recorded in the field. Cluster analysis of size-corrected data separated fish into three geographic groups: The Isle Royale, eastern (Michigan), and western regions (Michigan). Finer scales of stock structure were also suggested. Discriminant function analysis demonstrated that head measurements contributed to most of the observed variation. Cross-validation classification rates indicated that 67–71% of individual fish were correctly classified to their region of capture. This is the first study to present shape differences associated with location within a lake trout morphotype in Lake Superior.

  19. Geophysical investigation of sentinel lakes in Lake, Seminole, Orange, and Volusia Counties, Florida

    USGS Publications Warehouse

    Reich, Christopher; Flocks, James; Davis, Jeffrey

    2012-01-01

    This study was initiated in cooperation with the St. Johns River Water Management District (SJRWMD) to investigate groundwater and surface-water interaction in designated sentinel lakes in central Florida. Sentinel lakes are a SJRWMD established set of priority water bodies (lakes) for which minimum flows and levels (MFLs) are determined. Understanding both the structure and lithology beneath these lakes can ultimately lead to a better understanding of the MFLs and why water levels fluctuate in certain lakes more so than in other lakes. These sentinel lakes have become important water bodies to use as water-fluctuation indicators in the SJRWMD Minimum Flows and Levels program and will be used to define long-term hydrologic and ecologic performance measures. Geologic control on lake hydrology remains poorly understood in this study area. Therefore, the U.S. Geological Survey investigated 16 of the 21 water bodies on the SJRWMD priority list. Geologic information was obtained by the tandem use of high-resolution seismic profiling (HRSP) and direct-current (DC) resistivity profiling to isolate both the geologic framework (structure) and composition (lithology). Previous HRSP surveys from various lakes in the study area have been successful in identifying karst features, such as subsidence sinkholes. However, by using this method only, it is difficult to image highly irregular or chaotic surfaces, such as collapse sinkholes. Resistivity profiling was used to complement HRSP by detecting porosity change within fractured or collapsed structures and increase the ability to fully characterize the subsurface. Lake Saunders (Lake County) is an example of a lake composed of a series of north-south-trending sinkholes that have joined to form one lake body. HRSP shows surface depressions and deformation in the substrate. Resistivity data likewise show areas in the southern part of the lake where resistivity shifts abruptly from approximately 400 ohm meters (ohm-m) along the

  20. First annual report on the Biological Monitoring and Abatement Program at Oak Ridge National Laboratory

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Loar, J. M.; Adams, S. M.; Blaylock, B. G.

    1992-08-01

    As a condition of the National Pollutant Discharge Elimination System (NPDES) permit issued to Oak Ridge National Laboratory (ORNL) on April 1, 1986, a Biological Monitoring and Abatement Program (BMAP) was developed for White Oak Creek (WOC); selected tributaries of WOC, including Fifth Creek, First Creek, Melton Branch, and Northwest Tributary; and the Clinch River. BMAP consists of seven major tasks that address both radiological and nonradiological contaminants in the aquatic and terrestrial environs on-site and the aquatic environs off-site. These tasks are (1) toxicity monitoring; (2) bioaccumulation monitoring of nonradiological contaminants in aquatic biota; (3) biological indicator studies; (4)more » instream ecological monitoring; (5) assessment of contaminants in the terrestrial environment; (6) radioecology of WOC and White Oak Lake (WOL); and (7) contaminant transport, distribution, and fate in the WOC embayment-Clinch River-Watts Bar Reservoir system. This document, the first of a series of annual reports presenting the results of BMAP, describes studies that were conducted from March through December 1986.« less