• The 1931 eruption of Aniakchak volcano, Alaska: deposit characteristics and eruption dynamics

      Nicholson, Robert Stokes (2003-12)
      The 1931 eruption of Aniakchak progressed through several eruptive phases from multiple vents that totaled 1.4 x 10⁸ m³ dense rock equivalent of magma. The sequence of phases began with a sub-plinian eruption followed by a phreatomagmatically-influenced vulcanian phase originating from the primary vent. Effusive activity from two separate vents occurred simultaneously with the vulcanian phase. The eruption from the main vent progressed to strombolian in nature and eventually subsided into an effusive eruption. The composition of the magma ranged from trachydacite at the onset of the eruption to basaltic andesite at its conclusion. Volcanoes commonly exhibit variations in eruptive style similar to those seen at Aniakchak. Previous studies at other volcanoes have attributed changes in the nature of an eruption to such factors as the compositional variation in magma, magma flux, the presence of external water, conduit and surface morphology, and volatile degassing behavior. The differences in style of the 1931 Aniakchak eruption are the result of variations in magma flux, the presence or absence of external water, and differences in magma composition. Evidence of a zoned magma chamber indicates that properties associated with the magma chamber might have indirectly influenced the eruption style at Aniakchak.
    • The 1951 Bristol Bay salmon strike: isolation, independence and illusion in the last frontier

      McCullough, Nicole Susan (2001-12)
      Many people consider Alaska the last frontier, isolated and independent from the rest of the United States. An analysis of the salmon industry in Bristol Bay and a strike that occurred in 1951 cast doubt upon this belief. The labor dispute and preceding events paint a vivid picture of a population clearly dependent on a fishing industry controlled by absentee owners who manipulated events from Seattle and San Francisco. The strikers included Natives and Non-Natives who joined together to fight the powerful cannery owners and west coast unions who sought to expand their membership. Some of these unions had suspected communist members, and Alaska joined in the paranoia that seized the rest of the United States in their cold war fear of Communism. The strike and the actions of participants in the strike illustrate how Alaska's isolation and independence was but an illusion in the last frontier.
    • 2-D bed sediment transport modeling of a reach on the Sagavanirktok River, Alaska

      Ladines, Isaac A.; Toniolo, Horacio; Barnes, David; Schnabel, Bill (2019-05)
      Conducting a 2-D sediment transport modeling study on the Sagavanirktok River has offered great insight to bed sediment movement. During the summer of 2017, sediment excavation of two parallel trenches began in the Sagavanirktok River, in an effort to raise the road elevation of the Dalton Highway to remediate against future floods. To predict the time in which the trenches refill with upstream sediment a 2-D numerical model was used. Three scenarios: (1) a normal cumulative volumetric flow, (2) a max discharge event, and (3) a max cumulative volumetric flow, were coupled with three sediment transport equations: Parker, Wilcock-Crowe and Meyer Peter and Müller for a total of 9 simulations. Results indicated that scenario (1) predicted the longest time to fill, ranging from 1-6 years followed by scenario (2), an even shorter time, and scenario (3) showing sustained high flows have the capability to nearly refill the trenches in one year. Because the nature of this research is predictive, limitations exist as a function of assumptions made and the numerical model. Therefore, caution should be taken in analyzing the results. However, it is important to note that this is the first time estimates have been calculated for an extraction site to be refilled on the Sagavanirktok River. Such a model could be transformed into a tool to project filling of future material sites. Ultimately, this could expedite the permitting process, eliminating the need to move to a new site by returning to a site that has been refilled from upstream sediment.
    • 3-D modeling of interaction between a hydraulic fracture and multiple natural fractures using finite element analysis

      Talukder, Debashish; Awoleke, Obadare; Ahmadi, Mohabbat; Hanks, Catherine (2019-05)
      A three-layered, 3-D geo-mechanical model was developed using Finite Element Analysis (FEA) software (ABAQUS) to simulate single stage hydraulic fracturing treatment in a synthetic fractured model based on available shale information from literature. The main objectives of this study were- (i) to investigate the interaction between a hydraulic fracture (HF) orthogonally intersecting two parallel natural fractures (NF) and (ii) to identify significant parameters and their 2-factor interactions that affect HF propagation in the presence of multiple NFs. Based on literature review, an initial set of 20 parameters (a combination of geologic and drilling parameters) was selected. Those parameters were believed to affect the hydraulic fracture propagation in a naturally fractured model. Experiments were conducted in two stages. First-order order numerical experiments were conducted under the Plackett-Burman experimental design. Central Composite Design (CCD) was used to check curvature and to take care of non-linearity existing in the dataset. A stepwise sensitivity analysis and parametric study were conducted to identify significant parameters and their interactions. When the HF interacted with NFs, there were three possible outcomes- the HF either got arrested, dilated or crossed the NF. The overall hydraulic fracture geometry depended on the type of interaction behavior occurring at the intersection. The NF leakoff coefficient was the most significant factor in the 1st order experiments that affected the HF propagation in the presence of multiple NFs. CCD results suggested that NF strength at the bottom shale layer and injection fluid viscosity significantly influenced the HF opening in the presence of the natural fractures. The most significant two-factor interaction was the interaction between stress contrast and Young's modulus of the overburden shale (Ytop). This study will help understand the interaction behavior between a HF and two pre-existing NFs. The parametric study will provide a valuable insight for hydraulic fracturing treatment in a naturally fractured formation.
    • The 30-year outcome of assisted regeneration treatments in a burned and salvaged Interior Alaska boreal forest

      Allaby, Andrew; Juday, Glenn; Young, Brian; Yarie, John (2015-08)
      This study contributes to the understanding of the persistence of silvicultural treatments into the stem exclusion stage of forest development in an experiment originally designed to test the effectiveness of various white spruce (Picea glauca Moench [Voss]) regeneration practices. Many studies in the North American boreal forest address the effect of silvicultural treatments on a single tree species, specifically white spruce in the great majority of cases. The experiment measured in this study provided an excellent opportunity to compare treatment effects on white spruce density and growth. The Rosie Creek Fire Tree Regeneration Installation experiment represents an operational-scale, spatially-explicit, replicated design on a single site disturbed consecutively by high-severity wildfire and clearcut salvage harvest. Three hierarchical factors, each with multiple levels, were examined: landform type, ground scarification methods, and white spruce regeneration methods. All three of the experimental factors exercised continuing influence on the patterns of white spruce regeneration and growth. The treatment effects did not attenuate over time for white spruce, and we found statistically significant effects that the original researchers could only describe as tendencies. However, relatively few studies address treatment impacts on non-target species or determine how the silvicultural treatments affect a site's overall woody biomass production. Experimental silvicultural practices targeted in this study to improve white spruce survival had profound effects on other dominant upland tree species such as quaking aspen (Populus tremuloides Michx.) and Alaska birch (Betula neoalaskana Sarg.). Interior Alaska timber species demonstrate different regeneration strategies to post-disturbance environmental conditions, especially residual organic soil layer thickness and spatial configuration of surviving potential seed sources. Effective silvicultural practices must consider each species' unique reproductive biology, and clonal sprouting as a source of aspen persistence was a particularly important example in our study. Site differences, such as we found between the slope and ridge landforms, are a key consideration for implementing effective silvicultural practices. Significant interactions between the regeneration treatments and landform types proved to be critical to meet specific reforestation objectives, particularly the different herbaceous vegetation cover types, presence/absence of aspen clonal rootstocks, and spatial configurations regarding seed sources. Managing mixed species stands, which are common in the lightly managed portions of the boreal forest, requires not only the consideration of the future crop tree, but the interacting effects of silvicultural practices on all tree species.
    • 575 Tlingit verbs: a study of Tlingit verb paradigms

      Eggleston, Keri M. (2013-05)
      The Tlingit language, indigenous to Southeast Alaska and neighboring parts of British Columbia and the Yukon territory, is related to the Athabascan languages and the recently extinct language Eyak. Like Athabascan and Eyak, Tlingit verbal morphology is highly complex. The conjugation of Tlingit verbs is unpredictable in certain respects, making the documentation of verb forms from native speakers critical, due to the highly endangered state of the language, and because this has never before been documented for Tlingit. The objectives of the research presented here are twofold: 1) to document complete paradigms for 575 verbs, and; 2) to create a reference for second language learners and teachers of Tlingit. For each of the verbs included in the research, twelve modes were systematically documented through consultation with a group of native speakers. The newly documented forms were compiled into a database using Toolbox software and additionally organized into a user-friendly online database, hosted on the Goldbelt Heritage Foundation website. Based on the documented forms, descriptions of each of the twelve modes were written, with second language students and teachers as the target audience. The descriptions of each mode include information pertaining to the semantics, morphology, and verb stem variation, and are intended to assist second language learners in mastering the difficult task of conjugating Tlingit verbs. Another critical item included for each verb entry is the verb theme, which illustrates all of its component parts including thematic prefix, conjugation prefix, classifier, and stem. The accompanying detailed description of each element of the verb theme serves as a grammatical sketch of the Tlingit verb for language learners. An additional result of the research is a set of nine prefix combination charts. Because the Tlingit verb has many prefix positions, there are a number of regular contractions that take place in conjugating a verb. The prefix combination charts illustrate the regular contractions that take place between the thematic prefixes, conjugation prefixes, aspect prefixes, subject prefixes, and classifiers, to name a few. These charts show language learners how to switch between subject prefixes for a given verb.
    • 60,000 year climate and vegetation history of Southeast Alaska

      Wilcox, Paul S.; Fowell, Sarah; Bigelow, Nancy; Mann, Daniel; Dorale, Jeffrey (2017-08)
      Sedimentological and palynological analyses of lacustrine cores from Baker Island, located in Southeast Alaska's Alexander Archipelago, indicate that glaciers persisted on the island until ~14,500 cal yr. BP. However, the appearance of tree pollen, including Pinus cf. contorta ssp. contorta (shore pine) and Tsuga mertensiana (mountain hemlock) immediately following deglaciation suggests that a forest refugium may have been present on ice-free portions of neighboring islands or the adjacent continental shelf. Sedimentological and palynological analyses indicate a variable climate during the Younger Dryas interval between ~13,000 and ~11,500 cal yr. BP, with a cold and dry onset followed by ameliorating conditions during the latter half of the interval. An eight cm-thick black tephra dated to 13,500 ± 250 cal yr. BP is geochemically distinct from the Mt. Edgecumbe tephra and thus derived from a different volcano. Based on overall thickness, multiple normally graded beds, and grain size, I infer that the black tephra was emplaced by a large strombolian-style paroxysm. Because the dominant wind direction along this coast is from the west, the Addington Volcanic Field on the continental shelf, which would have been subaerially exposed during the eruption, is a potential source. The similarity in timing between this eruption and the Mt. Edgecumbe eruption suggests a shared trigger, possibly a response to unloading as the Cordilleran Ice Sheet retreated. To complement the Baker Island lacustrine record, a speleothem paleoclimate record based on δ¹³C and δ¹⁸O values spanning the interval from ~60,000 yr. BP to ~11,150 yr. BP was recovered from El Capitan Cave on neighboring Prince of Wales Island. More negative δ¹³C values are attributed to predominance of angiosperms in the vegetation above the cave at ~22,000 yr. BP and between ~53,000 and ~46,000 yr. BP while more positive δ¹³C values in speleothem EC-16-5-F indicate the presence of gymnosperms. These data suggest limited or no ice cover above El Capitan Cave for the duration of the record, possibly indicating that this region was a nunatak during glacial periods.
    • An 8 ka record of vegetation cover, fire history and moisture availability from North-Central Mongolia

      Molhoek, Emily (2007-05)
      Analysis of pollen, charcoal, and stable carbon and nitrogen isotopes ([delta]¹³C and [delta]¹⁵N) from a sediment core of Mongolian Lake Terhiyn-Tsagaan show increases in moisture availability coincident with mid- to late Holocene expansion of the Asian monsoon. The lake is freshwater and located in an intermontane depression on the flanks of the Hangai Range of north-central Mongolia. The site lies within the forest-steppe biome ~400 m below tree line. The low C:N of the sediments indicates that organic matter is primarily composed of autochthonous material. Artemisia and Chenopodiaceae pollen are indicators of dry steppe and semi-desert vegetation, whereas Poaceae pollen is more abundant in humid meadow-steppe or forest-steppe assemblages. An aridity index, calculated by dividing Artemisia + Chenopodiaceae by Poaceae pollen, is used to identify changes in moisture availability. High aridity indices and spikes of charcoal influx record relatively humid conditions at the site between 8.0 and 5.5 k years BP. Low charcoal influx rates and peak values of the aridity index between 4.5 and 4.0 k years BP correspond to a documented interval of drought in southern Asia and northern Africa attributed to a weak Asian monsoon. A decrease in charcoal influx since 7.5 k years BP combined with progressive increase in [delta]¹⁵N indicates increasing aridification from the mid-Holocene to nearly the present. Intervals of humidification at Lake Terhiyn-Tsagaan are thus synchronous with the waxing and waning of the Asian monsoon and out of phase with humid intervals recorded at Lake Telmen, approximately 250 km to the northwest. It is possible that the Terhiyn-Tsagaan drainage lies at the northern and/or western edge of the region that received precipitation from an expanded Holocene summer monsoon.
    • A Communication Perspective Of Alcoholism Recovery: Narratives Of Success

      Arlen, Kathryn Grace; Brown, Jin (2007)
      Understanding alcoholism and how it wreaks havoc upon the human condition has been and continues to be a prime concern for social scientists, psychologists, physicians, therapists, the legal system, a host of other concerned professionals, and society in general, particularly those who suffer from this "dis-ease" (Denzin, 1987a). Much past research has focused upon physiological concerns, suggesting disease, genetic, or even allergic connections. While such research certainly carries significant import and credibility, this study focuses on the social construction of the alcoholic identity and eventual evolution into a recovering identity. The methodology of narrative inquiry with conversational interviewing as method provides insight into six individuals' shifting perceptions of self and relationships from their alcoholic experiences to increasingly more viable social interactions and eventual positive self identity construction. Emergent themes focus on interactive social context, divided feelings toward alcohol, communication of individual responsibility, and realignment of human values.
    • A Comparative Analysis Of Mhc Genetic Diversity At The Class Ii Loci In Some Arctic Mammalian Species

      Wei, Zhengyu; Happ, George (2002)
      The genetic diversity at the Major Histocompatibility Complex (MHC) class II loci in some arctic mammalian species, musk ox, moose, caribou, and bears, have been characterized. The general objective of this study was to broaden the knowledge of the MHC polymorphism, selection, evolution and function in natural populations of arctic mammals. Allelic variation was assessed by analysis of MHC class II DR and DQ loci at exon 2 region. Sequences were amplified via the polymerase chain reaction (PCR), followed by either DNA sequencing after cloning of the PCR products or single-stranded conformation polymorphism (SSCP) analysis and sequencing. Monomorphism was observed at DRA, DRB, and DQA loci in both musk ox and moose, but relatively high polymorphism was observed at DQB locus. For the first time, four DQB alleles and one DQA allele were found identical in these two distantly related species which split approximately 23 million years ago, indicating stringent trans-species polymorphism. Both DRB and DQB seem to be functional by analyzing their cDNA expression. An intermediate level of MHC polymorphism at DRB locus was found in caribou and reindeer. Phylogenetic analysis of cervid DRB alleles indicated that all reindeer and caribou DRB alleles were from a monophyletic lineage, implying an ancient bottleneck in R. tarandus. High polymorphism at the DRB locus in polar bear was also observed. Four DRB alleles were found to be shared by polar bear and dog. The trans-species polymorphism of the shared alleles may have been persistent for 10 to 15 million years. Nine DQB alleles rather than two DRB alleles were also found in a pure domestic dog lineage of Doberman pinschers. These data imply that selection pressure may vary among MHC loci. In summary, the general level of MHC polymorphism at the class II loci is lower in herbivores (musk ox, moose, and caribou) than carnivores (polar bear). Biased selection may be applied on DQB locus. Stringent trans-species polymorphism between two distantly related species may be the result of persistent selection by shared parasites in the same environment.
    • A comparative study of contrasting structural styles in the range-front region of the northeastern Arctic National Wildlife Refuge, northeastern Brooks Range, Alaska

      Hanks, Catherine Leigh; Stone, David B.; Crowder, R. Keith; Keskinen, Mary J.; Watts, Keith W.; Ave Lallemant, Hans G.; Mull, C. G. (1991)
      The range front of the northeastern Brooks Range in the Arctic National Wildlife Refuge (ANWR) is defined by anticlinoria cored by a 'basement' complex of weakly metamorphosed sedimentary, volcanic and intrusive rocks. These anticlinoria are interpreted to reflect horses in a northward-propagating regional duplex between a floor thrust at depth in the 'basement' complex and a roof thrust near the base of the cover sequence. Lateral variations in the geometry of these range-front anticlinoria reflect changes in lithology and deformational style of both the 'basement' and its cover. Two distinct structural geometries are displayed along the range front of northeastern ANWR. To the east, the large range-front anticlinorium is interpreted to reflect multiple horses of Cenozoic age within the stratified, slightly metamorphosed sedimentary and volcanic rocks of the pre-Mississippian 'basement'. During Cenozoic thrusting, these mechanically heterogeneous rocks deformed primarily via thrusting and related folding with minor penetrative strain. The Mississippian and younger cover sequence shortened via both thrust duplication and detachment folding above a detachment in the Mississippian Kayak Shale. In contrast, to the west the pre-Mississippian rocks consist primarily of the mechanically homogeneous Devonian Okpilak batholith. The batholith was transported northward during Cenozoic thrusting and now forms a major topographic and structural high near the range front. The batholith probably shortened during thrusting as a homogeneous mass via penetrative strain. Because the Kayak Shale is thin to absent in the vicinity of the batholith, Mississippian and younger rocks remained attached to the batholith and shortened via penetrative strain and minor imbrication. These two range-front areas form the central portion of two regional transects through northeastern ANWR. General area-balanced models for both transects suggest that the amount of total shortening is governed by the structural topography and the geometry of the basal detachment surface. While the structural topography of northeastern ANWR is reasonably well-constrained, the geometry of the basal detachment is not. Given a range in reasonable basal detachment geometries, shortening in both transects ranges from 16% to 61%. Detailed balanced cross sections based on subsurface and surface geologic data yield 46-48% shortening for both transects.
    • A Comparison Of The Effects Of Analysis Techniques And Computer Systems In Remote Sensing Technology And A Reference Data Collection Technique

      Spencer, Joellen Page (1981)
      A technique for collecting and recording reference data which considers the spectral and spatial characteristics of Landsat data, the computer system being used, and the gradient nature of wildland vegetation was developed and described. Different analysis techniques for four critical factors affecting the accuracy of computer-aided analysis products were evaluated. Comparisons were made on the basis of accuracy evaluations of two methods of data/analyst interface, three methods of deriving training statistics, three methods of spectral class descriptions, and two levels of map category detail. The primary data set used was digital Landsat multispectral data for a study area around Fairbanks, Alaska. Reference data were developed from field work and photo-interpretation. The training methods compared were supervised, unsupervised, and modified clustering. The three spectral class description methods were: (1) labels derived from the training data; (2) the color display screen; and (3) from ground plot data. Community level cover types were compared with generalized map categories. The effect of post-classification stratification was evaluated. The reference data technique provides geographically located stands and cover types identifications with a flexible coding system that can be aggregated to correspond to the spectral data categories. No difference in classification accuracy was found for an experienced analyst using a printout oriented system such as EDITOR or a screen oriented system such as IDIMS. The modified cluster method of developing training statistics was more effective and efficient than supervised or unsupervised training methods. The use of ground plot data and subsequent stratification improved the descriptions of spectral classes. Generalized mapping categories were more accurate than detailed mapping categories. Knowledge of the ecologic, floristic, and spectral characteristics of the cover types in the study area is necessary to develop spectral class descriptions and stratification criteria.
    • A Computer Simulation Of Auroral Arc Formation

      Wagner, John Scott (1981)
      Recent satellite measurements have revealed two intriguing features associated with the formation of auroral arcs. The first is that an auroral arc is produced by a sheet of electrons accelerated along a geomagnetic field-aligned potential drop, and the second is that these electrons carry a field-aligned, upward directed electric current. In order to explain these measurements, a self-consistent, time dependent, computer simulation of auroral arc formation has been developed. The simulation demonstrates for the first time that a stable V-shaped potential structure, called an auroral double layer, develops spontaneously as a result of an ion shielded electron current sheet interacting with a conducting ionosphere. The double layer accelerates current-carrying electrons into the upper atmosphere at auroral energies. The double layer potential depends critically on the drift speed of the current-carrying electrons and on the temperature of the ambient shielding ions. Localized double layers occur near the ionosphere when the geomagnetic field is assumed to be uniform, but when a converging magnetic field is introduced, the double layer becomes extended due to the presence of an additional population of electrons trapped between the magnetic mirror and the double layer potential. The simulated auroral current sheet is subject to auroral curl and fold type deformations due to unstable Kelvin-Helmholtz waves. The previous incompletely understood auroral fold producing mechanism is described.
    • A Concept To Assess The Performance Of A Permafrost Model Run Fully Coupled With A Climate Model

      Paimazumder, Debasish (2009)
      Soil-temperatures simulated by the fully coupled Community Climate System Model LCM version 3.0 (CCSM3) are evaluated using three gridded Russian soil-temperature climatologies (1951-1980, 1961-1990, and 1971-2000) to assess the performance of permafrost and/or soil simulations. CCSM3 captures the annual phase of the soil-temperature cycle well, but not the amplitude. It provides slightly too high (low) soil-temperatures in winter (summer) with a better performance in summer than winter. In winter, soil-temperature biases reach up to 6 K. Simulated near-surface air temperatures agree well with the near-surface air temperatures from reanalysis data. Discrepancies in CCSM3-simulated near-surface air temperatures significantly correlate with discrepancies in CCSM3-simulated soil-temperatures, i.e. contribute to discrepancy in soil-temperature simulation. Evaluation of cloud-fraction by means of the International Satellite Cloud Climatology project data reveals that errors in simulated cloud fraction explain some of the soil-temperature discrepancies in summer. Evaluation by means of the Global Precipitation Climatology Centre data identifies inaccurately-simulated precipitation as a contributor to underestimating summer soil-temperatures. Comparison to snow-depth observations shows that overestimating snow-depth leads to winter soil-temperature overestimation. Sensitivity studies reveal that uncertainty in mineral-soil composition notably contributes to discrepancies between CCSM3-simulated and observed soil-temperature climatology while differences between the assumed vegetation in CCSM3 and the actual vegetation in nature marginally contribute to the discrepancies in soil-temperature. Out of the 6 K bias in CCSM3 soil-temperature simulation, about 2.5 K of the bias may result from the incorrect simulation of the observed forcing and about 2 K of the bias may be explained by uncertainties due network density in winter. This means that about 1.5 K winter-bias may result from measurement errors and/or model deficiencies. Overall, the performance of a permafrost/soil model fully coupled with a climate model depends partly on the permafrost/soil model itself, the accuracy of the forcing data and design of observational network.