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1دورية أكاديمية
المؤلفون: Shirzaei, Manoochehr, Freymueller, Jeffrey, Tornqvist, Torbjorn E., Galloway, Devin L., Dura, Tina, Minderhoud, Philip S. J.
المساهمون: Geosciences
الوصف: Measuring coastal subsidence is essential to evaluating hazards associated with sea-level rise. This Review discusses the processes driving coastal subsidence, space-borne and land-based measurement techniques, as well as models for simulating observed subsidence and predicting future trends. Coastal subsidence contributes to relative sea-level rise and exacerbates flooding hazards, with the at-risk population expected to triple by 2070. Natural processes of vertical land motion, such as tectonics, glacial isostatic adjustment and sediment compaction, as well as anthropogenic processes, such as fluid extraction, lead to globally variable subsidence rates. In this Review, we discuss the key physical processes driving vertical land motion in coastal areas. Use of space-borne and land-based techniques and the associated uncertainties for monitoring subsidence are examined, as are physics-based models used to explain contemporary subsidence rates and to obtain future projections. Steady and comparatively low rates of subsidence and uplift owing to tectonic processes and glacial isostatic adjustment can be assumed for the twenty-first century. By contrast, much higher and variable subsidence rates occur owing to compaction associated with sediment loading and fluid extraction, as well as large earthquakes. These rates can be up to two orders of magnitude higher than the present-day rate of global sea-level rise. Multi-objective predictive models are required to account for the underlying physical processes and socio-economic factors that drive subsidence. ; US National Aeronautics and Space AdministrationNational Aeronautics & Space Administration (NASA) [80NSSC170567, 80NSSC17K0566]; US National Science FoundationNational Science Foundation (NSF) [EAR-1735630, EAR-1349311, EAR-1624795, EAR-1624533]; EU Marie Skodowska-Curie Individual Fellowship [894476]; International Geoscience Programme (IGCP) project [639] ; Published version ; The authors thank the reviewers for providing insightful comments and suggestions ...
وصف الملف: application/pdf
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2دورية أكاديمية
المؤلفون: Cochran, William J., Spotila, James A., Prince, Philip S.
المساهمون: Geosciences
الوصف: The nature of the connection between the Eastern California shear zone (ECSZ) and the San Andreas fault (SAF) in southern California (western United States) is not well understood. Northwest of San Gorgonio Pass, strands of the ECSZ may be migrating south and west into the convergent zone of the San Bernardino Mountains (SBM) as it is advected to the southeast via the SAF. Using high-resolution topography and field mapping, this study aims to test whether diffuse faults within the SBM represent a nascent connection between the ECSZ and the SAF. Topographic resolution of <= 1 m was achieved using both lidar and unmanned aerial vehicle surveys along two Quaternary strike-slip faults. The Lone Valley fault enters the SBM from the north and may form an along-strike continuation of the Helendale fault. We find that its geomorphic expression is obscured where it crosses Quaternary alluvium, however, suggesting that it may have a low rate of yet-undetermined activity. The Lake Peak fault is located farther south and cuts through the high topography of the San Gorgonio massif and may merge with strands of the SAF system. We find that this fault clearly cuts Quaternary glacial deposits, although the magnitude of offset is difficult to assess. Based on our interpretation of geomorphic features, we propose that the Lake Peak fault has predominantly dextral or oblique-dextral motion, possibly with a slip rate that is comparable to the low rates observed along other strands of the ECSZ (i.e., <= 1 mm/yr). Comparing the geomorphic expressions of these faults is difficult, however, given that the erosive nature of the mountainous landscape in the SBM may obscure evidence of active faulting. Based on these observations, as well as the occurrence of other diffuse faults in the region, we suggest that dextral strain is overprinting the actively convergent zone of the SBM, thereby creating a throughgoing connection between the ECSZ and the SAF west of San Gorgonio Pass. ; National Science Foundation (NSF)National Science ...
وصف الملف: application/pdf
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3دورية أكاديمية
المؤلفون: Muñoz, Martha M., Hu, Y., Anderson, Philip S. L., Patek, S. N.
المساهمون: Biological Sciences
الوصف: The influence of biomechanics on the tempo and mode of morphological evolution is unresolved, yet is fundamental to organismal diversification. Across multiple four-bar linkage systems in animals, we discovered that rapid morphological evolution (tempo) is associated with mechanical sensitivity (strong correlation between a mechanical systems output and one or more of its components). Mechanical sensitivity is explained by size: the smallest link(s) are disproportionately affected by length changes and most strongly influence mechanical output. Rate of evolutionary change (tempo) is greatest in the smallest links and trait shifts across phylogeny (mode) occur exclusively via the influential, small links. Our findings illuminate the paradigms of many-to-one mapping, mechanical sensitivity, and constraints: tempo and mode are dominated by strong correlations that exemplify mechanical sensitivity, even in linkage systems known for exhibiting many-to-one mapping. Amidst myriad influences, mechanical sensitivity imparts distinct, predictable footprints on morphological diversity.
وصف الملف: application/pdf
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4دورية أكاديمية
المؤلفون: Jensen, Carrie K., McGuire, Kevin J., Prince, Philip S.
المساهمون: Forest Resources and Environmental Conservation, Geosciences, Virginia Water Resources Research Center
مصطلحات موضوعية: Water Resources, drainage density, flow intermittency, temporary streams, PERENNIAL FLOW INITIATION, NETWORK EXPANSION, WATER-QUALITY, MASS-BALANCE, CHANNEL, RIVERS, CONTRACTION, MANAGEMENT, STATE
الوصف: Understanding patterns of expansion, contraction, and disconnection of headwater stream length in diverse settings is invaluable for the effective management of water resources as well as for informing research in the hydrology, ecology, and biogeochemistry of temporary streams. More accurate mapping of the stream network and quantitative measures of flow duration in the vast headwater regions facilitate implementation of water quality regulation and other policies to protect waterways. We determined the length and connectivity of the wet stream and geomorphic channel network in three forested catchments (<75 ha) in each of four physiographic provinces of the Appalachian Highlands: the New England, Appalachian Plateau, Valley and Ridge, and Blue Ridge. We mapped wet stream length seven times at each catchment to characterize flow conditions between exceedance probabilities of <5% and >90% of the mean daily discharge. Stream network dynamics reflected geologic controls at both regional and local scales. Wet stream length was most variable at two Valley and Ridge catchments on a shale scarp slope and changed the least in the Blue Ridge. The density and source area of flow origins differed between the crystalline and sedimentary physiographic provinces, as the Appalachian Plateau and Valley and Ridge had fewer origins with much larger contributing areas than New England and the Blue Ridge. However, the length and surface connectivity of the wet stream depended on local lithology, geologic structure, and the distribution of surficial deposits such as boulders, glacially-derived material, and colluival debris or sediment valley fills. Several proxies indicate the magnitude of stream length dynamics, including bankfull channel width, network connectivity, the base flow index, and the ratio of geomorphic channel to wet stream length. Consideration of geologic characteristics at multiple spatial scales is imperative for future investigations of flow intermittency in headwaters. ; Published version
وصف الملف: 3350 - 3363 (14) page(s); application/pdf
العلاقة: http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000408341800004&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=930d57c9ac61a043676db62af60056c1Test; http://hdl.handle.net/10919/82489Test; https://doi.org/10.1002/hyp.11259Test; 31; 19; McGuire, Kevin J. [0000-0001-5751-3956]
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5دورية أكاديمية
المؤلفون: Lacy, Robert C., Miller, Philip S., Nyhus, Philip J., Pollak, J. P., Raboy, Becky E., Zeigler, Sara L.
المساهمون: Biological Sciences
الوصف: Wildlife population models have been criticized for their narrow disciplinary perspective when analyzing complexity in coupled biological physical human systems. We describe a metamodel approach to species risk assessment when diverse threats act at different spatiotemporal scales, interact in non-linear ways, and are addressed by distinct disciplines. A metamodel links discrete, individual models that depict components of a complex system, governing the flow of information among models and the sequence of simulated events. Each model simulates processes specific to its disciplinary realm while being informed of changes in other metamodel components by accessing common descriptors of the system, populations, and individuals. Interactions among models are revealed as emergent properties of the system. We introduce a new metamodel platform, both to further explain key elements of the metamodel approach and as an example that we hope will facilitate the development of other platforms for implementing metamodels in population biology, species risk assessments, and conservation planning. We present two examples one exploring the interactions of dispersal in metapopulations and the spread of infectious disease, the other examining predator-prey dynamics to illustrate how metamodels can reveal complex processes and unexpected patterns when population dynamics are linked to additional extrinsic factors. Metamodels provide a flexible, extensible method for expanding population viability analyses beyond models of isolated population demographics into more complete representations of the external and intrinsic threats that must be understood and managed for species conservation. ; Published version
وصف الملف: application/pdf
العلاقة: e84211; http://hdl.handle.net/10919/85380Test; https://doi.org/10.1371/journal.pone.0084211Test; 12
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6تقرير
المؤلفون: Ghommem, Mehdi, Hajj, Muhammad R., Watson, Layne T., Mook, Dean T., Snyder, Richard D., Beran, Philip S.
المساهمون: Computer Science
مصطلحات موضوعية: Algorithms, Data structures
الوصف: The kinematics of a flapping plate is optimized by combining the unsteady vortex lattice method with a deterministic global optimization algorithm. The design parameters are the amplitudes, the mean values, the frequencies, and the phase angles of the flapping motion. The results suggest that imposing a delay between the different oscillatory motions and controlling the way through which the wing rotates at the end of each half stroke would enhance the lift generation. The use of a general unsteady numerical aerodynamic model (UVLM) and the implementation of a deterministic global optimization algorithm provide guidance and a baseline for future efforts to identify optimal stroke trajectories for micro air vehicles with higher fidelity models.
وصف الملف: application/pdf
العلاقة: Computer Science Technical Reports; http://eprints.cs.vt.edu/archive/00001138Test/; http://hdl.handle.net/10919/19415Test; TR-10-18; http://eprints.cs.vt.edu/archive/00001138/01/dirMAO10.pdfTest
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7رسالة جامعية
المؤلفون: Prince, Philip S.
المساهمون: Geosciences, Spotila, James A., Henika, William S., Tracy, Robert J., Daniels, W. Lee, Ranson, William A.
مصطلحات موضوعية: landscape disequilibrium, base level, Passive margin, transient incision, stream capture, Blue Ridge, New River
الوصف: The mechanism through which the Appalachian Mountains have maintained moderate relief some ~300 Myr after the cessation of mountain building has long puzzled geomorphologists. As recent studies have shown that Appalachian exhumation has occurred at slow rates consistent with isostatic rebound of thickened crust, the driving forces behind localized episodes of accelerated incision and the associated rugged topography have been difficult to explain given the absence of tectonic uplift. This study uses previously undocumented relict fluvial gravels and knickpoint location to confirm the role of drainage rearrangement in producing local base level drop and subsequent basin-scale transient incision in the southern Appalachians. This process is fundamentally driven by the high potential energy of streams flowing across the elevated, slowly eroding Blue Ridge Plateau relative to the present Atlantic and landward interior base levels. Gravel deposits confirm that repeated capture of landward-draining Plateau streams by Atlantic basin streams, whose immediate base level is 250-300 m lower, forces episodic rapid incision and overall erosional retreat of the Blue Ridge Escarpment along the Plateau margin. The distribution of knickpoints, bedrock gorges, and relict surfaces in the interior of the Plateau indicate that the New River, which drains to the continental interior, is actively incising the low-relief Plateau surface due to episodic drops in landward base level. The origin of landward base level perturbation is unclear, but it may be the result of glacially-driven shortening and steepening of the lower New River during the Pleistocene. Collectively, these data indicate that rapid base level drop through drainage reorganization can energize streams in otherwise stable landscapes and accelerate fluvial incision and relief production without uplift of the land surface. This process is likely quite significant in post-orogenic settings, where inherited drainage patterns may not reflect the most direct, and thus ...
وصف الملف: application/pdf
العلاقة: etd-05062011-110218; http://hdl.handle.net/10919/77065Test; http://scholar.lib.vt.edu/theses/available/etd-05062011-110218Test/
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8رسالة جامعية
المؤلفون: Cook, Philip S.
المساهمون: Forestry
مصطلحات موضوعية: LD5655.V855 1986.C665, National parks and reserves -- Fees, User charges, Wilderness areas -- North Carolina -- Grandfather Mountain
جغرافية الموضوع: North Carolina
الوصف: User fees for federal Wilderness have been suggested as a way to reduce deficit spending on Wilderness recreation and supplement decreasing management budgets. This study examines the users of Linville Gorge Wilderness, a federal free area, and Grandfather Mountain Backcountry, a nearby private fee area, to determine if fees would exclude any socioeconomic or other user group who presently uses wilderness and determine if fees are acceptable to users. The study compares users' socioeconomic characteristics and travel cost demand functions and analyzes attitudes towards fees to determine the extent to which fees are likely to change use behavior. No difference is found in the socioeconomic characteristics of the users of the fee and the free area, suggesting fees excluding any for federal Wilderness are equitable, not excluding any socioeconomic group currently using Wilderness. The trip demand functions of the travel cost models for the two areas are statistically the same, suggesting users are making the same economic decision when visiting each area. Fees are found to be acceptable to users if Wilderness will deteriorate without fees and fee revenues are spent on Wilderness management. Users suggest about $25 for an annual Wilderness permit and about two dollars for a daily fee as reasonable amounts. Most users say the fee at Grandfather Mountain does not influence their decision to visit, suggesting fees will not greatly affect demand at federal Wilderness. The site demand function for Linville Gorge predicts a large decrease in demand, but this is common to most travel cost models and does not usually prove true. Further research of the travel cost model and the administrative feasibility of suggested fee levels is recommended. ; M.S.
وصف الملف: vii, 173 leaves; application/pdf
العلاقة: OCLC# 15190927; http://hdl.handle.net/10919/104313Test
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9رسالة جامعية
المؤلفون: Chilton, Kristin Danielle
المساهمون: Geosciences, Spotila, James A., Romans, Brian W., Eriksson, Kenneth A., Strom, Kyle Brent, Prince, Philip S.
مصطلحات موضوعية: landscape evolution, erodibility, knickpoints, boulders, topography, Appalachians
الوصف: Geomorphologists have long observed the influence of lithology on landscape form and evolution. However, the specific mechanisms by which this is accomplished are not well characterized. Here, I investigate the role of lithology in landscape evolution processes across spatial and temporal scales and geomorphic domains, to progress our understanding of the basic controls on the processes which shape Earth's surface. These investigations were carried out within the Valley and Ridge province of the Appalachian Mountains, where contrasts in strength of underlying lithologies (juxtaposed by Alleghanian deformation) exert a clear, dominant control on the fabric of the landscape, providing an excellent opportunity to study the influence of lithology on a variety of landscape evolution processes. First, I assess the geomorphic function of boulders found on hillslopes and channels in the Valley and Ridge province of the Appalachians, which are sourced from resistant lithologies capping ridgelines. High-resolution UAV surveys and field mapping of boulder distributions and characteristics reveal that boulders are abundant on hillslopes and highly concentrated in channels, often trap sediment upslope, and appear to be long-lived. These observations suggest that boulders act as armor for hillslopes and channels, shielding weaker underlying units from erosion and inhibiting fluvial incision, and therefore play an important role in preserving topography in the Valley and Ridge landscape, highlighting a specific mechanism by which lithology exerts an influence on topography in this setting. Second, I investigate the relative importance of rock strength and discontinuity spacing in setting fluvial bedrock erodibility by comparing knickpoint and non-knickpoint bedrock, which correspond to end-member erodibility cases, and assess how lithology impacts knickpoint expression. Detailed field surveys of 21 lithologic knickpoints, surrounding non-knickpoint reaches, and corresponding bedrock properties reveal three key outcomes: 1) ...
وصف الملف: ETD; application/pdf
العلاقة: vt_gsexam:32151; http://hdl.handle.net/10919/104740Test
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10رسالة جامعية
المؤلفون: Whalen, Lisa Marie
المساهمون: Geosciences, Gazel, Esteban, Caddick, Mark J., Prince, Philip S.
مصطلحات موضوعية: Large igneous province, Pangea, continental break-up, supercontinent
الوصف: The Central Atlantic Magmatic Province (CAMP) is the large igneous province (LIP) that coincides with the breakup of the supercontinent Pangea. Major and trace element data, Sr-Nd-Pb radiogenic isotopes, and high-precision olivine chemistry were collected on primitive CAMP dikes from Virginia (VA). These new samples were used in conjunction with a global CAMP data set to elucidate different mechanisms for supercontinent breakup and LIP formation. On the Eastern North American Margin, CAMP flows are found primarily in rift basins that can be divided into northern or southern groups based on differences in tectonic evolution, rifting history, and supercontinental inheritance. Geochemical signatures of CAMP suggest an upper mantle source modified by subduction processes. We propose that the greater number of accretionary events, or metasomatism by sediment melts as opposed to fluids on the northern versus the southern Laurentian margin during the formation of Pangea led to different subduction-related signatures in the mantle source of the northern versus southern CAMP lavas. CAMP samples have elevated Ni and low Ca in olivine phenocrysts indicating a significant pyroxenite component in the source, interpreted here as a result of subduction metasomatism. Different collisional styles during the Alleghanian orogeny in the North and South may have led to the diachroneity of the rifting of Pangea. Furthermore, due to a low angle of subduction, the Rheic Plate may have underplated the lithosphere then delaminated, triggering both the breakup of Pangea and the formation of CAMP. ; Master of Science
وصف الملف: ETD; application/pdf
العلاقة: vt_gsexam:8593; http://hdl.handle.net/10919/71423Test
النص الكامل