The lower continental slope of Morocco’s west coast consists of Triassic-age salt manifested in the form of diapirs, tongues, sheets, and canopies, and both extensional and compressional structures that result from salt movements. Salt diapirism and regional tectonics greatly influenced a broad spectrum of depositional processes along the margin. Mapping of a 1064-km2 (411-mi2) seismic survey acquired in the Safi Haute Mer area reveals that Jurassic to Holocene salt mobilization has induced sedimentation that manifests itself in gravity slumps and slides and debris flows. An east-west–trending structural anticline located downdip of the salt-influenced region, was activated during the Atlas uplift (latest Cretaceous) and shaped much of the lower continental slope morphology from Tertiary time until present. The largest of the mass transport deposits (MTC) is a 500-m (1640-ft)-thick Cretaceous-age unit that spans an area of up to 20,000 km2 (7722 mi2). Seismic facies composing the MTC are (1) chaotic, mounded reflectors; (2) imbricated continuous to discontinuous folded reflector packages interpreted to represent internal syn-depositional thrusts; and (3) isolated, thick packages of continuous reflectors interpreted to represent transported megablocks (3.3 km2 [1.3 mi2]). The latter show well preserved internal stratigraphy. The MTCs originated from an upslope collapse of a narrow shelf during the earliest phases of the Alpine orogeny. Seismic geomorphologic analysis of the non-salt-deformed sections reveal numerous linear features that are interpreted as migrating Mesozoic-age deepmarine sediment waves. Three styles of sediment waves have been identified. These include: (1) type J1—small (less than 17 m thick) and poorly imaged, Jurassic in age, ridges that have wavelengths of up to 12 km and crest-to-crest separations of less than 1 km; (2) type K1—early Aptian constructional sediment waves (~110 m thick) that appear to show some orientation and size variations which suggest an influence on currents by salt-influenced seafloor topography, and (3) type K2—latest Albian and earliest post-Albian sediment waves exhibiting wave heights of 40 m and crest-to-crest separations of 1 km, that are continuous across the entire study area and show evidence of up-slope migration.

The lower continental slope of Morocco’s west coast consists of Triassic-age salt manifested in the form of diapirs, tongues, sheets, and canopies, and both extensional and compressional structures that result from salt movements. Salt diapirism and regional tectonics greatly influenced a broad spectrum of depositional processes along the margin. Mapping of a 1064-km2 (411-mi2) seismic survey acquired in the Safi Haute Mer area reveals that Jurassic to Holocene salt mobilization has induced sedimentation that manifests itself in gravity slumps and slides and debris flows. An east-west–trending structural anticline located downdip of the salt-influenced region, was activated during the Atlas uplift (latest Cretaceous) and shaped much of the lower continental slope morphology from Tertiary time until present. The largest of the mass transport deposits (MTC) is a 500-m (1640-ft)-thick Cretaceous-age unit that spans an area of up to 20,000 km2 (7722 mi2). Seismic facies composing the MTC are (1) chaotic, mounded reflectors; (2) imbricated continuous to discontinuous folded reflector packages interpreted to represent internal syn-depositional thrusts; and (3) isolated, thick packages of continuous reflectors interpreted to represent transported megablocks (3.3 km2 [1.3 mi2]). The latter show well preserved internal stratigraphy. The MTCs originated from an upslope collapse of a narrow shelf during the earliest phases of the Alpine orogeny. Seismic geomorphologic analysis of the non-salt-deformed sections reveal numerous linear features that are interpreted as migrating Mesozoic-age deepmarine sediment waves. Three styles of sediment waves have been identified. These include: (1) type J1—small (less than 17 m thick) and poorly imaged, Jurassic in age, ridges that have wavelengths of up to 12 km and crest-to-crest separations of less than 1 km; (2) type K1—early Aptian constructional sediment waves (~110 m thick) that appear to show some orientation and size variations which suggest an influence on currents by salt-influenced seafloor topography, and (3) type K2—latest Albian and earliest post-Albian sediment waves exhibiting wave heights of 40 m and crest-to-crest separations of 1 km, that are continuous across the entire study area and show evidence of up-slope migration.

To aid in forest management, various approaches using Geographic Information Systems (GIS) have been used to identify the spatial distributions of relative slope instability. This study presents a systematic evaluation of three common slope instability modeling approaches applied in the Blue Ridge Mountains of Virginia. The modeling approaches include the Qualitative Map Combination, Bivariate Statistical Analysis, and the Shallow Landsliding Stability (SHALSTAB) model. Historically, the qualitative nature of the first model has led to the use of more quantitative statistical models and more deterministic physically-based models such as SHALSTAB. Although numerous studies have been performed utilizing each approach in various regions of the world, only a few comparisons of these approaches have been done in order to assess whether the quantitative and deterministic models result in better identification of instability. The goal of this study is to provide an assessment of relative model behavior and error potential in order to ascertain which model may be the most effective at identifying slope instability in a forest management context. The models are developed using both 10-meter and 30-meter elevation data and outputs are standardized and classified into instability classes (e.g. low instability to high instability). The outputs are compared with cross-tabulation tables based on the area (m²) assigned to each instability class and validated using known locations of debris flows. In addition, an assessment of the effects of varying source data (i.e. 10-meter vs. 30-meter) is performed. Among all models and using either resolution data, the Qualitative Map Combination correctly identifies the most debris flows. In addition, the Qualitative Map Combination is the best model in terms of correctly identifying debris flows while minimizing the classification of high instability in areas not affected by debris flows. The statistical model only performs well when using 10-meter data while SHALSTAB only performs well using 30-meter data. Overall, 30-meter elevation data predicts the location of debris flows better than 10-meter data due to the inclusion of more area into higher instability classes. Of the models, the statistical approach is the least sensitive to variations in source elevation data. / Master of Science

Debris flows can be considered the most significant geological hazard in areas of high relief in Scotland having impacted upon slope foot infrastructure several times in recent years. The potency of this geohazard is anticipated to increase over the coming decades due to a climatologically enforced upturn in debris flow frequency. In thisresearch material and topographic controls on debris flow activity are investigated using a combination of field and laboratory based analysis of debris flows at six study sites across upland Scotland. Centrifuge modelling is also used to simulate theinitiation of debris flows in soils with varying particle size distributions.Spatial densities of debris flow measured in the field indicate that hillslopes underlain by sandstone and granitic bedrocks, which tend to be mantled by coarser sand rich soils, have a greater frequency of flows than those underlain by schist andextrusive lava bedrocks. Higher debris flow densities on slopes underlain by sandstone and granite lithologies are facilitated by high permeability in overlying regolith matrixes allowing more rapid increase in pore water pressures duringrainstorms although this is likely to be further influenced by packing and organic content. Centrifuge modelling of hillslope debris flows also demonstrate that sandier soils are generally geotechnically more susceptible to slope failure.The susceptibility of a hillslope to debris flow is strongly influenced by slope geometry and morphology. Hillslopes with persistently steep slopes and a high incidence of concavities, gullies and couloirs are topographically more predisposed todebris flow activity due to greater shear stresses and morphologically controlled, gravity induced concentrations of hillslope hydrology. The majority of material in channelised debris flows is entrained during the gully propagation stage of the massmovement. Consequently, such events can be considered accumulative channelised debris flows. Longer and steeper gullies with greater sediment capacities are more likely to yield larger flow mass movements. Coupling between open hillslopes andbedrock gullies is shown to be an essential component for conceptualisation of the debris flow geohazard.Due to the role they play in amplifying debris flow magnitude, hazard management should be focussed around bedrock gullies and stream channels. Highesthazard rankings should be assigned to slope foot infrastructure in proximity to gullied stream channels with high sediment capacities and long, steep profiles conducive to large accumulative channelised debris flows. To avoid detrimental aesthetic impact, hazard management should be strongly geared towards utilisation of lower impactexposure reduction techniques and less visually intrusive engineering approaches such as increasing culvert capacity to accommodate debris flows. During realignment or the planning of future transport infrastructure, culverts with capacities significantly exceeding those required for purely hydrodynamic considerations should be placed straight on to stream channels avoiding proximal gully bends.

The West Elk Breccia has been studied since the late 1800’s with many interpretations regarding its origin. One unrecognized possibility is that parts of it are debris-avalanche deposits. This study has recognized evidence for this interpretation at three scales: volcano scale, outcrop scale, and intra-outcrop scale. At the volcano scale, a scarp in the old volcano reveals underlying Mesozoic bedrock, suggesting sector collapse. At the outcrop scale, megablocks of the original edifice, up to hundreds of meters in length, have atypical orientations and are surrounded by a gravel matrix. At the intra-outcrop scale, jigsaw-fit fracturing and rip-up clasts are common in distal deposits, which are documented in analogous debris-avalanche deposits. Similar to the debris-avalanche deposit at Mt. Shasta, medial-to-distal-matrix volcaniclast content decreases by 23%; Paleozoic and Mesozoic clasts increase by 5%; and the size of megablocks decreases. The geochemical and petrographic signatures reveal breccia blocks composed of pyroxene-andesite, a more silicic matrix facies, and the andesitic-to-dacitic East Elk Creek Tuff, all compositions that corroborate previous work on this northern extension of the San Juan volcanic field. Measured sections in the 100-km² study area allow for an estimation of total formation volume of approximately 8.5 km3.

L’histoire géologique récente de Mars reste peu étudiée, comparativement à l’histoire « primitive » de Mars (>3,5 Ga). Cependant, l’arrivée de nouvelles images haute résolution a permis d’identifier la présence de ravines à la surface de terrains très récents. Dans ce travail, nous nous sommes attaché à caractériser la morphologie des ravines et les processus qui les ont générés. Ces nouvelles observations relancent la question de la présence d’eau liquide actuellement à la surface de Mars que ce soit à l’état pur ou sous forme de mélange (saumure, coulée de débris...). Des simulations expérimentales en chambre froide à la pression atmosphérique de Mars et de la Terre ont été menées. Elles ont notamment permis de quantifier le rôle de la teneur en eau dans la couche active du pergélisol sur le mécanisme de formation des ravines et leur mobilité. Nous avons également décrit l’évolution saisonnière de petits réseaux ramifiés qui se sont développés chaque année au printemps durant la période 2007-2012. / The recent geological history of Mars remains poorly studied, in comparison to theearly history of Mars (>3,5 Ga). However, the acquisition of new high-resolution imagesallowed to identified the presence of gullies on the surface of recent landforms such asdunes. In this work, we focused on characterizing the morphology of gullies and theirprocess(es) of formation. These new observations revive the issue of the presence of liquid water present on the surface of Mars than either pure or as a mixture (brine, debris flow ...). Experimental simulations in a cold room at Martian and terrestrial atmospheric pressure have been conducted. In particular, they allowed us to quantify the role of water content in the active layer of the permafrost in order to better constrain the mechanism of formation of gullies and their motion. We also described the seasonal evolution of small branched networks developed at spring during the 2007-2012 period.

Orientador: Fábio Augusto Gomes Vieira Reis / Resumo: As corridas de detritos são fenômenos naturais que podem ser vistos no mundo todo. Tratam-se de processos de movimentos de massa onde ocorre o escoamento rápido do material e comumente está associado aos altos índices pluviométricos e/ou variáveis do meio físico. A Serra do Mar possui características geomorfológicas e climáticas que torna a região potencialmente favorável a esse tipo de evento. A catástrofe ocorrida em fevereiro de 1994 em Cubatão (SP) trouxe diversos danos, tanto econômicos como sociais. Embora sejam processos que atingem muitas regiões, a previsão ainda é bastante complicada. Assim, este trabalho tem como objetivo a análise da potencialidade a corridas de detritos em sub-bacias, focando-se nos resultados dos cálculos dos índices e parâmetros morfométricos e, também, associados aos níveis de precipitação. Para tal, selecionou-se 13 sub-bacias que foram afetadas na região de Cubatão (SP) em fevereiro de 1994. Os dados foram obtidos em escala 1:50.000, salvo pelas feições que foram mapeadas na fotografia aérea em escala 1:25.000 que foram realizadas após o evento. O estudo das feições foi baseado em sua distribuição espacial, ou seja, em sua área em relação a área de cada sub-bacia, de modo a possibilitar a comparação com os resultados dos índices e parâmetros morfométricos. A sub-bacia número 04 (que engloba a RPBC, atingida pelo evento) mostrou-se a de maior potencialidade em toda a área de estudo. Posto isto, através dos resultados obtidos, conclui-se que o... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Debris flows are natural phenomenal that can be seen all over the world. This are about mass movement processes where the material quickly flows, commonly associated to high rainfall levels and/or another environmental variables. The geomorphological and climatic features of Serra do Mar makes the region potentiality favorable to this kind of events. The catastrophe that occurred in Cubatão (SP) in February/1994 resulted in several economic and social loss. Although these processes smite many regions, it is extremely difficult to predict them. Thus, this dissertation aims to analyze the debris flow potentiality into sub-basins, focusing on morphometric indexes and parameters calculations combined with precipitation levels. For this study 13 sub-basins were selected, and all of them were affected by the 1994 event. The data were obtained in a 1:50.000 scale, and the features was mapped using aerial photography, 1:25.000 scale, shot after the landslides in 1994. The features study was based in its spatial distribution, relating the scarring and the sub-basin areas, and then comparing them with the calculated indexes abd morphometric parameters. After studying all 13 areas the sub-basin number 04 (that includes RPBC that was smote by the event) was the one that showed grater potentiality. Therefore, throught the results obtained, it is concluded that indexes and morphometric parameters are an important tool to identify and evaluate potentiality in debris-flows areas. / Mestre

Orientador: Paulina Setti Riedel / Banca: Nelson Ferreira Fernandes / Banca: Antonio Miguel Vieira Monteiro / Banca: Ana Paula Dutra Aguiar / Banca: Leandro Eugenio da Silva Cerri / Resumo: Um modelo dinamico com caracteristicas friccionais, que utiliza como parametros basicos o angulo de atrito interno do material ( int Ó ) e basal ( bed Ó ) com a superficie onde ocorre o movimento, foi calibrado e aplicado com objetivo de simular as mesmas condicoes em que ocorreram corridas de massa nos anos de 1985, 1994 e 1999, em tres bacias da Serra do Mar, na regiao de Cubatao (SP-Brasil), na escala 1:10.000. Um modelo estatico de estabilidade por talude infinito, definido atraves do indice de estabilidade (SI), foi aplicado para subsidiar o estudo de areas com potencial aos processos de escorregamentos translacionais rasos, que podem evoluir para corridas de massa. Um inventario de cicatrizes tambem foi elaborado a partir da interpretacao de produtos de sensoriamento remoto, utilizado para validar o modelo estatico, assim como para definir pilhas de materiais deflagradas no modelo dinamico. Os resultados com o modelo estatico mostraram-se mais adequados quando se utilizaram as unidades litologicas para variacao dos parametros geotecnicos. Mais de 85% das cicatrizes ficaram dentro dos limites inferior de estabilidade e superior de instabilidade. As simulacoes com o modelo dinamico permitiram criar diferentes cenarios, com caracteristicas como trajetoria e alcance do material mobilizado, semelhantes aos eventos ocorridos no passado. Para tal modelo, diferentes configuracoes de pilhas de materiais e variacoes do angulo de atrito basal, em funcao do mapa de materiais, permitiram simulacoes mais realistas. / Abstract: A dynamic model with frictional characteristics that uses as basic parameters internal friction angle of the material ( int Ó ) and bed friction angle ( bed Ó ) with the surface where movement occurs was calibrated and applied to simulate the same conditions under which debris flows occurred in the years 1985, 1994 and 1999, in three watersheds of the Serra do Mar, in the region of Cubatao (Sao Paulo, Brasil), on a scale of 1:10.000. A static model of infinite slope stability, defined using the stability index (SI), was applied to inform the study of areas that have potential for processes of shallow translational landsliding that could evolve into debris flows. Landslide inventory data was also elaborated based on the interpretation of remote sensing products, used to validate the static model as well as to define deflagrated pile material in the dynamic model. The results with the static model proved to be more satisfactory when the lithological boundaries were used for variation of the geotechnical parameters. More than 85% of the scarps were within the lower threshold stability and upper threshold instability. The simulations with the dynamic model allowed the creation of different scenarios with characteristics, such as trajectory and range of the mobilized material, similar to the events that occurred in the past. For this model, different configurations of pile material and variations in the bed friction angle, as a function of the materials map, made it possible to carry out more realistic simulations. / Doutor

The Green River canyons of the eastern Uinta Mountains have experienced a 5- year period of high debris flow activity. Catchment factors were studied in watersheds and on debris fans with recent debris flows, leading to the development of a conceptual framework of the hillslope and debris flow processes that deliver sediment to the Green River. Two recent fan deposits were monitored to determine the magnitude and processes of reworking that occur during mainstem floods of varying magnitude. The dominant debris flow initiation mechanism, termed the firehose effect, occurs when overland flow generated on bedrock slopes cascades down steep cliffs and saturates and impacts colluvium stored in bedrock hollows, causing failure. The dry climate and high strength of bedrock cause hillslopes to be weathering-limited, prohibiting the formation of extensive regolith and vegetative cover. This reduces the degree vegetation regulates geomorphic processes and causes wildfire to have little influence on debris flow initiation. The dry climate and strong rocks also lead to high runoff ratios and steep escarpments that result in debris flow initiation via the firehose effect. This initiation process also dominates in Grand Canyon, where geologic and topographic characteristics are similar, but differs from locations in the Rocky Mountains where fire has a strong influence on debris flow processes. Monitoring of two recently aggraded debris fans shows that mainstem floods with magnitudes as low as 75% of the pre-dam 2-year flood cause significant erosion of fan deposits, whereas floods with magnitudes less than 40% of the pre-dam 2-year flood do little reworking. Armoring of the debris fan surface limited the degree ofreworking done by successive floods. Eroded material was deposited directly downstream of the fan, not at the expansion gravel bar. This depositional location represents a change in the organization of the fan-eddy complex, potentially altering the location of recirculating eddies and associated backwater habitats. These results indicate that the firehose effect may be the dominant initiation processes in the steep canyons of the Colorado Plateau and that dam releases that significantly rework fan deposits are within the operational range of large dams in the Colorado River system.

The stratigraphic record of lahars in the Whangaehu River reveals that in the past 180,000 years this route has been one of the main conduits for lahars from Mount Ruapehu, the highest active andesitic stratovolcano in the Central North Island of New Zealand. Both debris flows and hyperconcentrated flows have engulfed surfaces up to 160 km distance from the Volcano. Eight episodes of laharic activity are recognized by the distinctive lithology and similar age of their deposits. The newly defined upper Pleistocene Whangaehu Formation provides evidence for the earliest lahar event in the Valley, c. 180,000- 140,000 years ago. There is only meagre evidence for laharic activity following this event until the Ohakean and Holocene, although two new informally named deposits - the Mangatipona pumice sand (c. 37,000 years B.P.) and Apitian lahars (c. 32,000-25,500 years B.P) - are recognized, of minor extent. The formerly defined late Quaternary Te Heuheu (c. 25,500- 14,700 years B.P.), Tangatu (c. 14,700-5,370 years B.P.), Manutahi (c. 5 ,370-3,4600 years B.P.), Mangaio (c. 4,600 years B.P.) and Onetapu (< c. 1,850 years B.P.) Formations are here described and interpreted. Triggering mechanisms for lahar deposits are distinguished based on lithological criteria. (a) Bouldery deposits in the Whangaehu Formation are interpreted to have been emplaced by a single highly competent debris flow triggered by a southerly-directed flank collapse at Mount Ruapehu. This debris flow was competent enough to transport boulders up to 2 m in diameter over 140 km from the Volcano. Bouldery deposits are also recognized in the Onetapu Formation, but are restricted to higher gradient surfaces on the Mount Ruapehu ring plain. The Onetapu Formation deposits are interpreted to have been emplaced by lahars resulting from catastrophic drainage of Crater Lake, which occupies the active crater on Mount Ruapehu. (b) Pebbly and sandy deposits are interpreted to have been emplaced by low competence debris flows and hyperconcentrated flows. These lahar deposits are recognized in all formations described. The lithology in these deposits is commonly pumice and they are interpreted to have been triggered by eruptions and/or high rainfall events at the Volcano. Formations, and individual members within Formations, were dated by radiocarbon dating of organic material found below, within or above lahar deposits, or by coverbed stratigraphy. Both rhyolitic and andesitic tephras provided recognizable time planes in the late Quaternary coverbeds overlying lahar deposits. In this study quantitative analysis of quartz abundance, which is shown to vary between loesses and palaeosols, is used as an indirect means of establishing a surrogate for past climate changes which have been correlated to the deep sea oxygen isotope curve. A minimum age for the newly defined Whangaehu Formation is established by this method. The accumulation rate for lahars in the Whangaehu River has accelerated from 1 km3 every c. 23,000 years in the past c. 160,000 years to 1 km3 in 589 years in the past c. 2,000 years. This acceleration probably results from the increased frequency of lahars in the River following the development of Crater Lake c. 2,000 years B.P. According to this pattern an estimated 0.17 km3 volume of lahars could be anticipated over the next 100 years. If the 2,000 year accumulation rate were to be met over the next 100 years there would be 170 lahars of l0[superscript]6 m3 in this time interval , or 17 lahars of 10[superscript]7 m3 (or 1.7 lahars of 10[superscript]8 m3). The largest reported volume for an historic lahar is 10[superscript]6 m3 and these have occurred on average once every 30 years. The accumulation rate for historic lahars is 0.0054 km3 in 100 years. Therefore, although the accumulation rate appears to have slowed down, further large lahars with magnitudes 10 or 100 times greater than those witnessed could be expected.