<p> The increased surface melting of the outlet glaciers of the Vatnaj&ouml;kull Ice Cap has a profound affect on the dynamics of the ice-bed couple and landform genesis. Soft-bedded glaciers are largely inaccessible, which creates a problem. One challenge is to understand the complex interactions of the glacier bed and its resultant depositional and deformational landform systems. This study investigates an outlet glacier from the Vatnaj&ouml;kull Ice Cap, described herein as the Fl&aacute;aj&ouml;kull glacier system. To circumvent some of these problems, three separate projects were conducted in this dissertation: (1) magnetic fabric study of effective pressure (difference between the ice-overburden pressure and pore-water pressure) and shear rate (glacier velocity) using a laboratory ring-shear device; (2) glaciological analysis of magnetic fabrics and c-axis orientations of dirty ice veins; and (3) investigation of drumlin formation using magnetic till fabrics and field relationships. Several hypotheses were addressed for each of these studies, which include: (1) to determine if fabric strength is independent of shear rate and effective pressure. This hypothesis was tested and the results confirmed that the fabric strength (S1 eigenvalue) was independent of shear rate and effective pressure. Based on these results, effective pressure and shear rate cannot be interpreted from fabric strength evidence from glacial deposits; (2) in the glaciological study, I hypothesized that the dirty ice veins were sub-vertically sheared from the bed near the ice front, but then moderately deformed. Results from the magnetic fabrics indicate that the maximum K1 susceptibility axis (77&deg; plunge) is approximately parallel to the vein margins verify that the injection was sub-vertical. The long axes of the recrystallized ice grains (parallel to foliation plane defined by K₁ &ndash; K₂) appeared to show a good correlation with the plunge of the maximum K₁ susceptibility. Also, the eigenvector plunge of the c-axes was approximately normal to the shear plane, which supports previous theory that c-axes rotate away from the shear plane toward the vertical. Multi-maximum girdle fabrics from the c-axes and associated textures from thin sections (e.g. nucleated grains, bulging of grain boundaries and slips band) suggest that some deformation likely occurred after emplacement; and (3) the Boulton hypothesis was tested using magnetic till fabrics and field relationships. According to this idea, drumlins form due to hydrologic heterogeneity (permeability differences in granular materials) causing a solid nucleus to form in the bed where sediment is accreted and sheared in the direction of ice flow. At Fl&aacute;aj&ouml;kull, the magnetic fabrics from sites B and C mimicked the glacier flow direction with the longitudinal flow plane (K₁ &ndash; K₃) approximately parallel to the NNW-SSE drumlin long axis. The drumlin cores consisted of outwash sand and gravels which likely acted as rigid obstacles in the bed. Ice overriding resulted in heterogeneous deformation of the drumlin cores following the deposition of the upper basal till carapace. These results support the Boulton hypothesis. </p><p> These studies demonstrate significant progress toward understanding fabric strength development of soft-bedded glaciers. In linking studies (1) and (3) the ring-shear device was used to provide insights into fabric strength development upon shear rate and effective pressure. In the third study previous ring-shear experiments, magnetic till fabrics and field relationships were used to understand modern drumlin genesis.</p>

<p> Reports an investigation of the effects of chemical and physical weathering on submerged karst surfaces that pairs laboratory studies with computer modeling studies. The first study attempts to quantify the production of carbonate fines; soluble sediments produced by the incomplete dissolution of karst minerals during chemical weathering. Results show carbonate fine production in relation to dissolutional action; <i>Chalk:</i> 42.8%; <i>Coquina:</i> 2.6%; <i>Dolomite:</i> 3.1%; <i>Gray Limestone:</i> 4.8%; <i> Ocala Limestone:</i> 3.1%; <i>Shell Limestone:</i> 6.1%; <i> Travertine:</i> 8.6%. Due to the use of hydrochloric acid as opposed to carbonic acid these results may not be fully valid for application to natural speleogenic processes. The Limestone Weathering Model, a numerical-computer model, was developed using these experimental findings as minimal values compared with published rates. Reported as the actual volume of rock mass lost to both dissolution and to carbonate fine production, the rates for carbonate fine production ranged from 5.8% to 10.9% (year 1-5.8%, year 2-8.5%, year 3-9.7%, year 4-10.3%, year 5-10.9%), with a mean value for carbonate fine production of 9%, but a continuing rate after five years approaching 11%. The second study uses metrological laser scanning to measure the erosive loss due hydraulic shearing force and corrasion on submerged limestone surfaces. The rates for material removed using increasing velocity values (0.3m/s, 0.5m/s, 1.0m/s, 1.5m/s, 2.0 m/s, 2.5m/s) during flow durations of less than 6 minutes duration were : 1) Hydraulic shearing force- 0.3&micro;m/s, 0.5&micro;m/s, 0.4-1.7&micro;m/s, 2.5 &micro;m/s, 5.5 &micro;m/s, 2) Corrasion- 0.3 &micro;m/s, 0.7 &micro;m/s, 1.5 &micro;m/s, 1.5-1.8 &micro;m/s, 8.9 &micro;m/s, 8.1 &micro;m/s. The study model was modified to return these rates for hydraulic shearing force limited by the depth of the chemical corrosion of the surface. The model returns % rock volume lost to hydraulic shearing force compared to dissolutional rate (1mm/y) for 3 flow velocities (0.03m/s&lt;, 1.0m/s&lt;, 2.5m/s&lt;) on 4 timing schedules: Annual- 7.8,14.3,19.6, Semiannual- 21.1,21.1,69.7, Quarterly- 32.8,43.6, 70.9, Monthly- 80.0, 109.3, 200.3. Model demonstrates significant effect (7.8% to 200% over dissolutional rate) on speleogenic rates from even infrequent, moderate changes in flow velocities due to storm events. Investigation&rsquo;s results support the significance of chemical weathering by disaggregation and physical weathering by hydraulic shearing force as major factors in the processes of karst speleogenesis.</p>

<p> In the face of accelerating sea-level rise, people continue to live near and develop the coast. In the United States, we have chosen adaptation and protection, via coastal defenses, over retreat from the coast despite the unsustainable nature of efforts to rebuild our towns after storms. Coastal resilience has emerged as the dominant post-disaster narrative and has reinvigorated efforts to help our coasts recover from storms, but the application of theory-based principles of coastal resilience remains unclear. Here, I show that coastal resilience plans incorporate theory-based elements of coastal resilience significantly more than beach management plans. I reviewed over 3,000 pages in 22 planning documents and recorded use of 27 management techniques in five categories associated with coastal resilience. A Mann-Whiney U test found that resilience plans (n = 10) contained significantly more (p &lt; 0.05) techniques than beach management plans (n = 12) overall, but none of the differences in plan scores was significant when examined by category of technique. This research uncovers inadequacies of the current level of adaptation for sea-level rise, challenges the current process of coastal land use planning, and suggests improvements municipalities can implement to maximize impacts of coastal resilience planning such as developing holistic, diverse plans that include socioeconomic resilience and collaboration between practitioners and theorists.</p><p>

The aim of this thesis is to establish the evolutionary history of relict talus accumulations in the Scottish Highlands through study of their distribution, morphology, structure and sedimentology, and through dating and pollen analysis of buried soil horizons. Analyses of talus morphology demonstrates that though the investigated slopes comprise a basal concavity and upper straight slope, features hitherto interpreted as characteristic of unmodified rockfall accumulations, there is considerable variability in upper slope gradient. Surface relief indicates widespread reworking by slope failure, gullying and debris flows. Sections through gully-side exposures exhibit up to 3.5 m of stacked debris flow deposits, wash layers and buried soils overlying rockfall deposits, indicating a complex history of sediment reworking. Sedimentological analyses indicate that 27-30% of the talus sediments at one site (Trottemish) comprise fine (< 2 mm) particles representing granular weathering of the rockwall and syndepositional accumulation of both fine and coarse debris. The volume of talus on Trottemish implies an average rockwall retreat rate of c. 0.3 mm yr-1 since deglaciation, of which 0.08-0.09 mm yr-1 reflects granular weathering rather than rockfall. Failure and reworking of talus is inferred to reflect reduced infiltration rates (and high porewater pressures during rainstorms) caused by progressive accumulation of fines. Radiocarbon dating of buried soils indicates that reworking commenced prior to c. 6 cal ka BP, and has been intermittently active during the Holocene. Pollen analyses and charcoal concentration counts provide no evidence for accelerated reworking as a result of anthropogenic interference with vegetation cover, but the timing of reworking events provides support for enhanced activity associated with climatic deterioration after c. 2.7-2.3 cal ka BP. The characteristics of the investigated slopes show that models that treat talus as a free-draining accumulation of rockfall debris have limited applicability, and an alternative model that incorporates progressive reworking by other processes is proposed.

The aim of this study is to seek for a more detailed understanding of the geomorphology of some parts of Central Saudi Arabia, on the basis of aerial photographic interpretation, field surveys and investigation, and data obtained by field and laboratory analysis. An introduction to the study area is given together with an account of the geology and physiography of Saudi Arabia and especially the study area based upon drilling, field studies, and records from a variety of sources. A procedure for geomorphological mapping is discussed together with a review of the principles, problems, methods, and development of geomorphological mapping. Following these principles and methods, geomorphological maps have been compiled on the basis of the interpretation of air photographs, field surveys, and investigation, and laboratory analysis of surface materials. An attempt has been made to compare the method of geomorphological mapping with the results of landform classification including discussion of the application of the Land System approach to the area. The landform classification has been tabulated and the maps are presented to show the major landform systems and units with sample area showing the smaller units (landform type units) of the landforms. Particle size analysis and pebble shape were employed to give some information about deposition and transportation on selected pediments and alluvial fans. A discussion and critical reviews of relevant literature on the theory of sieving and sedimentation are given, This is followed by an introduction to the procedure for field and laboratory methods of particle size analysis and pebble shape measurements. The terminology for piedmont surfaces is discussed to clarify some of the confusion concerning the use of such terms. This is followed by a review of the theories concerning pediment formation, development, and their relationships to other landforms. The particle sizes of samples taken from pediments and the shapes of pebbles derived from these pediments have been measured, analysed, and discussed in relation to pediment, slope, distance from the mountain fronts and depth. Alluvial fans are another type of the landforms which are discussed in detail. They are well developed in the south-western parts of the study area where they form a series of confluent alluvial fans (bahada). Terminology and the theory of fan formation is discussed on the basis of field investigation and aerial photographic interpretation together with reviews of relevant literature. Size analysis of fan deposits as well as pebble shape are once again used to obtain information about transportation and deposition. Finally these studies are considered in relation to indications of climatic changes within Central Saudi Arabia. Problems of geomorphological mapping and interpretation are discussed and short accounts given of future work needed for detailed understanding of the desert landscape through the regional analysis of the landforms of a part of Central Saudi Arabia (conclusions).

No description available.

River mouths are characterised by a conflict between marine and fluvial processes, in which the planimetry of the mouth is dependent on the relative contribution of wave, tide and current, which may be manifested in spit and barrier accumulation forms, and the often opposing force of river discharge. Analysis of historical geomorphological evidence shows that the Donmouth has a history of constant change. In 1975-74, in order to assess the relative importance of fluvial and marine factors in explaining this change, monthly and seasonal tacheometric and sediment sampling was undertaken on the spit-bar which extends north across the mouth, and on the updrift beach. The dynamics of both form and material were measured. Hydro™ . graphic surveys of the estuary, nearshore and offshore morphology and material, and measurements of waves and currents were also conducted in the field. Field'data was analysed in_the laboratory and-by computer to produce quantitative results which serve to complement the qualitative description,. Results of the various analyses serve to illustrate a model example of rlver-mouth variability and dynamic equilibrium. The Donmouth Is located in a stretch of soft coastline characterised by a strong south to north wave and current energy continuum, which is reflected in northerly increases in elements of beach, nearshore and offshore form, process and material, out of the wave shadow provided by the rock headland at the southern extremity of th© bay. a s part of this continuum, the Donmouth is largely characterised by a marine-formed spit-bar, whose dimensions are dependent on the level of river and estuarine discharge. Models of spit-bar variability and of river-mouth planimetry were thus facilitated and are presented.

A região central da Amazônia encontra-se no interior da maior bacia de drenagem do planeta. Nas bacias dos rios Uatumã e Urubu, localizadas nesta região, o relevo apresenta drenagens com longos trechos retilíneos, inflexões abruptas, mudanças de curso evidenciadas por meandros abandonados, assimetrias de bacias, além de variações suavesdos padrões de dissecção e rugosidade, que são feições morfológicas sugestivas da ação de atividade tectônica moderna no seu modelado. Geologicamente, a área de estudo é coberta por sedimentos terciários seccionados por falhas normais e juntas. De modo a se identificar a influência de estruturas geológicas em superfície e subsuperfície sobre o relevo, aplicou-se no modelo digital de elevação da SRTM técnicas geomorfométricas que foram separadas em dois grupos: 1) assimetria de bacia, isobase e sinuosidade de canais usadas para revelar a gênesede formas do relevo, e 2) rugosidade (geometria fractal), densidade da rede drenagem e semivariograma utilizadas para verificar a distribuição espacial da rugosidade, dissecção e elevação. Além disso, as tendências direcionais do relevo também foram examinadas pela anisotropia da elevação (semivariograma), rugosidade (geometria fractal de autoafinidade) e densidade da rede de drenagem (geometria fractal de autosimilaridade). Os resultados do primeiro grupo permitiram delinear 9 domínios geomorfológicos que mostram rumos preferenciais de migração e, possivelmente, relação com basculamento de blocos. A comparação dos limites desses domínios com dadosgeológicos e geofísicos sugere que esses limites provavelmente se relacionam com falhas em subsuperfície, as quais teriam controlado a geração de falhas mais novas e o modelado do relevo da região. Tal fato é corroborado pela correspondência entre falhas em subsuperfície e superfície com os limites e as formas dos domínios, a mudança de sinuosidade de rios ao cruzar os limites e a relação da região com alta concentração de atividade sísmica ao longo de um dos limites. Outros dados geomorfológicos também apontam o controle estrutural do relevo. É o caso da relaçãoentre a orientação e aproximação das linhas no mapa de isobase com as falhas normais de alto ângulo mapeadas nas várzeas dos principais rios. Para o grupo 2, os resultados mostram a coincidência espacial entre domínios, definidos pela análise da rugosidade (dimensão fractal) e da elevação (semivariograma), e estruturas geológicas em subsuperfície. Este é o caso da área de Silves, onde a topografia colinosa apresenta diversos rios anelares e radiais, denotando condicionamento por falhas e dobras mapeadas por levantamentos sísmicos. Outro exemplo de tal influência é a associação de altos magnéticos com baixos padrões de dissecção mapeados pela análise da densidade da rede de drenagem. Além da distribuição espacial, as tendências direcionais dessas variáveis geomorfométricas foram analisadas e comparadas entre si e também com informações geológicas. Os resultados indicam que as direções predominantes para o maior eixo da anisotropia de elevação são NNE-SSW e NE-SW para as regiões de interflúvio, além de NW-SE para as planícies aluvionares. A direção de maior aglomeração da rede de drenagem, mostrada por sua anisotropia, coincide com atual campo de esforços da região investigada, exceto nas planícies de inundação. A direção com maior rugosidade, NNE-SSW, está presente na região de Presidente Figueiredo e é coincidente com a direção de cachoeiras e corredeiras. / The central region of the Amazon is located within the largest drainage basin in the world. In the basins of the Uatumã and Urubu rivers in this region, the landscape have drainages with long straight stretches, abrupt inflections, course changes evidenced by abandoned meanders, and basin asymmetries, and smooth variations of the landscape dissection and roughness patterns, which are morphological features suggestive of the action of modern tectonic activity. Geologically, the study area is covered by Tertiary sediments that are cut by normal faults and joints. To identify the influence of surface and subsurface geological structures on relief, we applied geomorphometric techniques on the digital elevation model from SRTM. These techniques have been separated into two groups: 1) basin asymmetry, isobase and river sinuosity were used for reveal the genesis of relief forms, and 2) fractal geometry, drainage density and semivariogram were used to verify the spatial distribution of the roughness, dissection and elevation. Furthermore, the trend-surfaces were also observed by elevation (semivariograma), roughness (self-affine fractal geometry) and drainage density anisotropy (self-similarity fractal geometry). The results of the first group permited the delineation of nine geomorphological domains that exhibit preferential migration paths and a potential relationship to block tilting. The comparison of the boundaries of these domains with geological and geophysical data suggests that these boundaries are likely related to subsurface faults that would have controlled the generation of younger faults and the relief modelling of the region. This interpretation is confirmed by the correspondence between subsurface and surface faults and the boundaries and shapes of the domains, the change in the sinuosity of rivers when crossing boundaries, and the effects of a high concentration of seismic activity along one of the limits on the region. Other geomorphological data also indicate structural control of the relief. There is a relationship between the orientation and approximation of the isobase map lines and the high-angle normal faults mapped in the floodplains of the main rivers. For the second group of variables, the results reveal the spatial coincidence between domains, defined by the analysis of roughness (fractal dimension) and elevation (semivariogram), and subsurface geological structures. This is the case in the area of Silves, where the undulating relief exhibits drainage with annular and radial patterns, coinciding with faults and folds previously mapped by seismic surveys. Another example of such influence is the combination of high magnetic with low dissection pattern mapped by drainage density. In addition to the spatial distribution, trends of these geomorphometric variables were compared among themselves and also with geological information. The results indicate that the predominant directions of the major anisotropy axis is NNE-SSW and NE-SW for the interfluve regions, and NW-SE to the alluvial plains. The direction of higher clustering of the drainage network, shown by its anisotropy, coincides with the modern stress field in the region investigated, except in flood plains. The direction with higher roughness, NNE-SSW, is present in the region of Presidente Figueiredo and is coincident with the direction of waterfalls and rapids.

Made available in DSpace on 2014-06-11T19:27:50Z (GMT). No. of bitstreams: 0 Previous issue date: 2004-12-08Bitstream added on 2014-06-13T20:17:18Z : No. of bitstreams: 1 hardt_r_me_rcla.pdf: 2354441 bytes, checksum: 5d7b098d2f45f52f55b6db7efc7a5358 (MD5) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / O trabalho aqui apresentado tem como cenário de estudo a Serra do Calcário, posicionada no município de Cocalinho (MT), e teve por objetivo caracterizar geomorfologicamente o relevo cárstico ali observado, propor um modelo explicativo da sua evolução e, conseqüentemente, fornecer subsídios para a compreensão do relevo cárstico desenvolvido na região Centro-Oeste do Brasil. A fundamentação teórica que norteou esta pesquisa foi a abordagem sistêmica, mais precisamente a ótica do sistema aberto do tipo processo-resposta. Neste contexto seguiu-se a orientação de Scheidegger, segundo a qual a paisagem pode ser entendida como um sistema dinâmico composto pela inter-relação de cinco princípios: Antagonismo, Instabilidade, Catena, Seleção e Controle Estrutural. Com base nesta fundamentação teórica e em trabalhos de campo e de gabinete, onde se destacam a interpretação de imagens de Satélite e Radar, foi possível a identificação de duas zonas e de cinco unidades geomorfológicas, bem como a proposição de uma seqüência evolutiva para o relevo da área em apreço. / This thesis is based on a study conducted in the Serra do Calcário(Limestone Mountain Range), located in the county of Cocalinho in the state of Mato Grosso; it was designed to provide a description of the geomorphology of the karst features observed and propose a model to explain its development, in an attempt to promote the understanding of the karst features found in the central-western part of Brazil. The theoretical background orienting the research was a systemic approach, specifically that of an open system of a process-response type. In the process-response open system approach adopted, the work of Scheidegger suggests that such features can be understood as part of a dynamic system based on the interrelationship of 5 principles: Antagonism, Instability, Catena, Selection and Structural Control. Based on this theoretical foundation, as well as work in the field and laboratory interpretation of satellite and radar images, it was possible to identify two zones and 5 geomorphologic features, as well as proposing a developmental sequence for the surface features of the area in question.

<p> Landslides represent a serious hazard to people and property in the Pacific Northwest. Currently, the factors leading to sudden catastrophic failure vs. gradual slow creeping are not well understood. Utilizing high-resolution monitoring techniques at a sub-annual temporal scale can help researchers better understand the mechanics of mass wasting processes and possibly lead to better mitigation of their danger. This research used historical imagery analysis, precipitation data, aerial lidar analysis, Structure from Motion (SfM) photogrammetry, terrestrial laser scanning (TLS), and hydrologic measurements to monitor displacement of the Silt Creek Landslide in the western Cascade Mountain Range in Linn County, Oregon. This landslide complex is ~4 km long by ~400 m wide. The lower portion of the landslide reactivated following failure of an internal scarp in June 2014. Precipitation was measured on site and historical precipitation data was determined from a nearby SNOTEL site. Analysis of aerial lidar data found that the internal scarp failure deposited around 1.00 x 10⁶ <i> m</i>³ of material over an area of 1.20 x 10⁵ <i> m</i>² at the uppermost portion of the reactivated slide. Aerial lidar analysis also found that displacement rates on the slide surface were as high as 3 <i>m/yr</i> during the 2015 water year, which was the year immediately following the failure. At the beginning of the 2016 water year, very low altitude aerial images were collected and used to produce point cloud data, via SfM, of a deformed gravel road which spans a portion of the reactivated slide. The SfM data were complimentary to the aerial and TLS scans. The SfM point cloud had an average point density of > 7500 points per square meter. The resulting cloud was manipulated in 3D software to produce a model of the road prior to deformation. This was then compared to the original deformed model. Average displacement found in the deformed gravel road was 7.5 m over the 17 months between the scarp failure and the collection of the images, or ~3 <i>m/yr</i>. TLS point clouds were collected quarterly over the course of the 2016 water year at six locations along the eastern margin of the reactivated portion of the landslide. These 3D point cloud models of the landslide surface had an average density of 175 points per square meter. Scans were georeferenced to UTM coordinates and relative alignment of the scans was accomplished by first using the iterative closest point algorithm to align stable, off-slide terrain, and then applying the same rigid body translation to the entire scan. This was repeated for each scan at each location. Landmarks, such as tree trunks, were then manually selected at each location and their coordinates were recorded from the initial scan and each successive scan to measure displacement vectors. Average annual displacement for the 2016 water year ranged from a maximum of 0.92 <i>m/yr</i> in the uppermost studied area of the slide, to a low of 0.1 <i>m/yr</i> at the toe. Average standard deviation of the vectors of features on stable areas was 0.039 m, corresponding to a minimum detectable displacement of about &plusmn;4 cm. Displacement totals decreased with increasing distance downslope from the internal scarp failure. Additionally, displacement tended to increase with increasing distance laterally onto the slide body away from the right margin at all locations except the uppermost, where displacement rates were relatively uniform for all landmarks. Volumetric discharge measurements were collected for Silt Creek in 2016 using salt dilution gauging and found that discharge in the upslope portion of the study area wwas ~1 <i>m3/s</i> and increased to ~1.6 <i>m3/s</i> in the downslope portion. Landslide displacement rates were found to be much lower during the 2016 water year than during the 2015 water year, despite higher precipitation. This suggests that the over-all displacement trend was decoupled from precipitation values. Displacement rates at all locations on the slide decreased with each successive scan period with some portions of the landslide stopping by autumn of 2016, suggesting the study captured the slide as it returned to a state of stability. The spatial and temporal pattern of displacement is consistent with the interpretation that the landslide reactivation was a response to the undrained load applied by the internal scarp failure. This finding highlights the importance of detailed landslide monitoring to improve hazard estimation and quantification of landslide mechanics. (Abstract shortened by ProQuest.) </p><p>