Earth Sciences Commons^™

Three-Dimensional Mechanics Of Yakutat Convergence In The Southern Alaskan Plate Corner, Peter O. Koons, B. P. Hooks, T. Pavlis, P. Upton, A. D. Barker

Earth Science Faculty Scholarship

Three-dimensional numerical models are used to investigate the mechanical evolution of the southern Alaskan plate corner where the Yakutat and the Pacific plates converge on the North American plate. The evolving model plate boundary consists of Convergent, Lateral, and Subduction subboundaries with flow separation of incoming material into upward or downward trajectories forming dual, nonlinear advective thermal/mechanical anomalies that fix the position of major subaerial mountain belts. The model convergent subboundary evolves into two teleconnected orogens: Inlet and Outlet orogens form at locations that correspond with the St. Elias and the Central Alaska Range, respectively, linked to the East by …

A Flume Experiment On The Effect Of Constriction Shape On The Formation Of Forced Pools, Douglas M. Thompson, C. R. Mccarrick

Physics, Astronomy and Geophysics Faculty Publications

A series of 18 flume runs were conducted in a 6-m long, 0.5-m wide recirculating flume with a bed gradient of 0.8% to determine the influence of obstruction shape on the formation and characteristics of forced pools. Six different-shaped obstructions were added to the flume with the maximum width of the obstruction held constant at 20 cm, which equaled a 40% constriction of flow. The obstruction shapes used included a square, a rectangle, a right triangle with the hypotenuse-facing upstream, a right triangle with the hypotenuse-facing downstream, a combination of a square and triangle with the hypotenuse-facing upstream, and a …

Assessing The Impact Of An Organic Restoration Structure On Boat Wake Energy, Jean Ellis, Douglas Sherman, Bernard Bauer, Jeffrey Hart

Jean Taylor Ellis

No abstract provided.

Protocols For Characterizing Aeolian Mass-Flux Profiles, Jean Ellis, Bailiang Li, Eugene Farrell, Douglas Sherman

Jean Taylor Ellis

No abstract provided.

Measuring The Transport Of Aeolian Sand With A Microphone System, Jean Ellis, Rebecca Morrison, Barry Priest

Jean Taylor Ellis

No abstract provided.

Depth Compensation For Pressure Transducer Measurements Of Boat Wakes, Jean Ellis, Douglas Sherman, Bernard Bauer

Jean Taylor Ellis

No abstract provided.

Retention Of Beach Sands By Dams And Debris Basins In Southern California, Douglas Sherman, Kamron Barron, Jean Ellis

Jean Taylor Ellis

No abstract provided.

Effects Of Sampling Frequency On Wave Characterization, Jean Ellis, Douglas Sherman

Jean Taylor Ellis

No abstract provided.

A Coastal Environment Field And Laboratory Activity For An Undergraduate Geomorphology Course, Jean Ellis, Paul Rindfleisch

Jean Taylor Ellis

A field and laboratory exercise for an undergraduate geomorphology class is described that focuses on the beach. The project requires one day of fieldwork and two laboratory sessions. In the field, students measure water surface fluctuations (waves) with a pressure sensor, survey beach profiles, collect sediment samples, and observe the beach state. In the laboratory, students wash and dry sediments, complete a grain size analysis, and determine sediment volumes. Students produce a report that includes analysis of wave data and beach profiles and a discussion of their findings.

Wave Transformation Across A Rock Platform, Belinho, Portugal, Eugene Farrell, Helena Granja, Lorenzo Cappietti, Jean Ellis, Bailiang Li, Douglas Sherman

Jean Taylor Ellis

No abstract provided.

Deconvolution Of U Channel Magnetometer Data: Experimental Study Of Accuracy, Resolution, And Stability Of Different Inversion Methods, Mike J. Jackson, Julie A. Bowles, Ioan Lascu, Peter A. Solheid

Geosciences Faculty Articles

We explore the effects of sampling density, signal/noise ratios, and position-dependent measurement errors on deconvolution calculations for u channel magnetometer data, using a combination of experimental and numerical approaches. Experiments involve a synthetic sample set made by setting hydraulic cement in a 30-cm u channel and slicing the hardened material into ~2-cm lengths, and a natural lake sediment u channel sample. The cement segments can be magnetized and measured individually, and reassembled for continuous u channel measurement and deconvolution; the lake sediment channel was first measured continuously and then sliced into discrete samples for individual measurement. Each continuous data set …

Collaborative Research: Grounding-Line Retreat In The Southern Ross Sea - Constraints From Scott Glacier, Brenda L. Hall

University of Maine Office of Research Administration: Grant Reports

This award supports a project to investigate late Pleistocene and Holocene changes in Scott Glacier, a key outlet glacier that flows directly into the Ross Sea just west of the present-day West Antarctic Ice Sheet (WAIS) grounding line. The overarching goals are to understand changes in WAIS configuration in the Ross Sea sector at and since the last glacial maximum (LGM) and to determine whether Holocene retreat observed in the Ross Embayment has ended or if it is still ongoing. To address these goals, moraine and drift sequences associated with Scott Glacier will be mapped and dated and ice thickness, …

Physical And Chemical Properties Of Ice In A Main Valley Glacier And A Tributary Glacier, Gornergletscher, Canton Valais, Switzerland, Annika M. Quick

Theses and Dissertations

Glacier models often fail to incorporate the geometry and/or physical properties of tributaries included in complex glaciers. Tributary glaciers have different source areas and flow conditions than the adjacent main valley glacier. Ice cores (~3m depth) and surface samples (<0.5m depth) were collected from Grenzgletscher (main valley glacier) and Zwillingsgletscher (tributary glacier) in the Gornergletscher system of the Swiss Alps. Stable water isotopes indicate seasonal variation, showing 1-2 annual layers. The mean d18O for Grenzgletscher is ~4.8‰ lower than for Zwillingsgletscher. This difference may be accounted for in part by elevation differences between the accumulation areas (~1.1‰ δ18O), increased avalanching in Grenzgletscher (~1.8 ‰ δ18O), and by varying climatic conditions at the time of precipitation (~0.9-1.4‰ variation in δ18O). Using a kinematic ice flow model, core ages were estimated using effective annual layer thickness (based on seasonal variations), annual accumulation rate and ice thickness. The Grenzgletscher core is ~4 years older than the Zwillingsgletscher core. Based on ages and flow distances, the tributary has a lower flow velocity (63-87 m/yr) compared to Grenzgletscher (61-134 m/yr). To understand thermal properties of the tributary, a 775 m GPR survey (200 MHz) was conducted along a flow line of Zwillingsgletscher. Topographic waves (ogives) observed on the surface are mimicked by the onset of reflectivity 10-20 m below the surface. Reflective regions are interpreted as warmer ice at the pressure melting point, overlain by colder ice. This thermal structure is likely related to acceleration through an ice fall. Since most tributary glaciers include ice falls, thermal properties of tributary glaciers may be different from those of the main valley glacier. The properties and geometry of tributary glaciers are significantly different from main valley glaciers and should therefore be incorporated into glacier models in the future.

Evaluating Efficacy Of Restoration Techniques, Keys View Road Reconstruction, Joshua Tree National Park, California, U.S.A, Scott R. Abella, E. Cayenne Engel

Public Policy and Leadership Faculty Publications

Keys View Road in Joshua Tree National Park (JOTR) was recently repaved, resulting in a buffer of vegetation and soil disturbance along the road corridor. In order to mitigate the effects of the repaving, JOTR designed an experimental framework to test various revegetation strategies. They outplanted salvaged and nursery grown native plant species in conjunction with vertical mulch in a fully crossed design (outplanting only, vertical mulch only, outplanting + vertical mulch, bare ground) to examine if any of the treatments most efficiently establish native plant communities.

Ground-Penetrating-Radar Reflection Attenuation Tomography With An Adaptive Mesh, Emily A. Hinz, John H. Bradford

CGISS Publications and Presentations

Ground-penetrating radar (GPR) attenuation-difference analysis can be a useful tool for studying fluid transport in the subsurface. Surface-based reflection attenuation-difference tomography poses a number of challenges that are not faced by crosshole attenuation surveys. We create and analyze a synthetic attenuation-difference GPR data set to determine methods for processing amplitude changes and inverting for conductivity differences from reflection data sets. Instead of using a traditional grid-based inversion, we use a data-driven adaptive-meshing algorithm to alter the model space and to create amore even distribution of resolution. Adaptive meshing provides a method for improving the resolution of the model space while …

Water Erosion Hazard Assessment Of The Lort And Young Rivers Catchment, Karen Holmes, John Andrew Simons, B Marillier, N Callow, Paul Galloway

Resource management technical reports

No abstract provided.

Rock Magnetic And Remanence Properties Of Both Synthetic Martian Basaltic Intrusions And Dropstones Along The East Antarctic Margin, To Aid In The Understanding Of The Carriers Of Crustal Magnetic Anomalies, David Michael Cuomo Jr.

Theses, Dissertations and Culminating Projects

This thesis examines potential carriers of magnetic anomalies found in remote areas where direct sampling is impossible. The areas examined are the southern hemisphere of Mars and the East Antarctic Margin. We examine the rock magnetic and remanence properties of synthetic Mars basalts and Antarctic dropstones, to predict the type and intensity of anomaly they would produce.

The anomalies measured within the Martian crust are entirely remanent magnetization and are remarkably orders of magnitude stronger than the strongest terrestrial anomaly. Two basalt compositions denoted M-type and T-type, deemed relevant to the crust of Mars, were synthesized to examine contrasts in …

Droughtscape- Summer 2010, Kelly Smith

Droughtscape, Quarterly Newsletter of NDMC, 2007-

Upcoming Workshops

Mild Drought Season Likely to Persist

Drought Impacts Intensify in Upper Midwest

Visiting Scientists

North Carolina Takes Drought Monitor Seriously

International Work- Murcia, Spain, June

The Toll Of Toxics: Investigating Environmental Contaminants, Donald Sparling, Barnett A. Rattner, John S. Barclay

USGS Staff -- Published Research

Two recent events [the Deepwater Horizon oil spill and the Asarco settlement] bring to the fore the work of wildlife toxicologists. Focusing on amphibians, reptiles, birds, and mammals, wildlife toxicology is a component of ecotoxicology--the study of toxic effects caused by natural or synthetic pollutants on living organisms and other constituents of ecosystems (Truhaut 1977). Now a distinct discipline within the wildlife profession-practiced by members of The Wildlife Society's own Wildlife Toxicology Working Group, among others-wildlife toxicology has become increasingly important as human populations and industry have spread, causing contaminants to multiply.

Emerging Environmental Contaminants (EECs) include an array of …

Arctic Landscapes In Transition: Responses To Thawing Permafrost, James P. Mcnamara

Geosciences Faculty Publications and Presentations

Observations indicate that over the past several decades, geomorphic processes in the Arctic have been changing or intensifying. Coastal erosion, which currently supplies most of the sediment and carbon to the Arctic Ocean [Rachold et al., 2000], may have doubled since 1955 [Mars and Houseknecht, 2007]. Further inland, expansion of channel networks [Toniolo et al., 2009] and increased river bank erosion [Costard et al., 2007] have been attributed to warming. Lakes, ponds, and wetlands appear to be more dynamic, growing in some areas, shrinking in others, and changing distribution across lowland regions …