Une partie de la region de Paspebiac a ete recouverte par deux glaces contemporaines, lors du dernier stade glaciaire du Wisconsinien. Une premiere s'est ecoulee du nord-nord-ouest, a recouvert la partie ouest de la region a l'etude et a erige une grande moraine laterale nord-sud a sa marge orientale; il n'a pu etre determine si cette glace etait l'inlandsis laurentidien ou une calotte gaspesienne. Une seconde glace progressant vers le nord-ouest a englace le sud-est du territoire et a construit une moraine terminale ouest-est, perpendiculaire et jointive a la premiere moraine. Un lac proglaciaire s'est forme a l'encoignure des deux glaces et a recouvert une partie d'un plateau demeure deglace au nord-est. Lors du dernier rechauffement climatique, le front de la glace du sud a regresse le premier, avant que la mer de Goldthwait noit les basses terres jusqu'a 46 metres vers 12 200 BP. Alors seulement, l'autre glace decouvre a son tour le territoire a l'etude. L'emersion est rapide, et certains elements laissent croire que les terres sont de nouveau transgressees depuis quelques millenaires.

Les Andes de Mérida (Venezuela) est caractérisé par la présence de morphologie glaciaire bien préservée entre 2400-4978 m. Les études de ces morphologies glaciares font la contribution pour mieux comprendre et reconstruire la Dernière Glaciation aux Andes Vénézuéliennes. La reconstruction de la Dernière Glaciation (connue dans la région comme Glaciation Mérida) était limitée par la disponibilité de chronologie glaciaire. Cette thèse fait sa contribution à la reconstruction de la Dernière Glaciation et à la connaissance du paléoclimat depuis le Pléistocène Superieur. La méthodologie a involucré l´analyse géomorphologique et l´étude géochronologique. La morphologie glaciaire a été datée avec la technique de nucléides cosmogéniques produits in-situ (10Be). Cette technique est appropriée pour dater les matériels riches en quartz et la période d´intérêt. Les inférences des conditions paleoclimatiques ont été faites sur la base des analyses de la paléo ELA.Des différentes dynamiques glaciares ont été identifiées aux Andes centrales de Mérida. Dans les vallées de Mucubají et Mucuchache, la dynamique a été caractérisée par plusieurs étapes de avancé-arrêt des glaciaires dans un recul général de la glace. Dans les vallées de Gavidia et Mifafí, la disparition des glaciares a été très rapide avec la vitesse de recul plus haute (entre 4-7 km/ky). Divers caractéristiques morpho métriques comme la pente du fond de la vallée, la topographie de la zone d´accumulation (cirques glaciares avec les murs très incliné), des surfaces de la zone d´accumulation et son orientation ont aussi contrôlé les différents dynamiques glaciares.Les avancées des glaciares ont été identifiées entre 2500-4200 m. Les avancées glaciares pendant le MIS 3 ont été reconnues à Sierra Nevada. Ces avancées ont été liées aux hautes précipitations dans le nord de l´Amérique de Sud produites par l´activité de la Zone de Convergence Intertropical. Ces avancées ont été aussi reliées aux conditions plus chaudes et humides dans l´Hémisphère Nord (aussi ces conditions ont été identifiées aux Andes vénézuéliennes et sont connues comme l´Interstadío El Pedregal). Les avancées glaciares pendant le Dernière Maximum Glaciares ont été enregistrées en Sierra Nevada á Mucubají et Las Tapias entre 3100-3600 m. Principalement, les avancées glaciares MIS 2 sont arrivées pendant l´Oldest Dryas-El Caballo Estadío à 17 ka. Ces avancées glaciares ont été reliées aux températures froides dans l´Hémisphère Nord et les températures plus froides enregistrées dans les carottes de glaciares tropicaux.Mots clésDatation par cosmogéniques produits in-situ, morphologie glaciaire, Pléistocène, Dernière Glaciation, LGM, paléo ELA. / The central Mérida Andes (Venezuela) landscape is characterized by the presence of well-preserved glacial landforms located between 2400 and 4978 m a.s.l. Geomorphological studies of these glacial landforms significantly contribute to the Venezuelan Andes glaciations reconstructions. However, Last Glaciation (locally called Mérida Glaciation) was poorly reconstructed because of limited chronological data. This dissertation attempts to contribute to the Last Glaciation reconstruction and paleoclimate knowledge since the late Pleistocene. Accordance this necessity, the methodology involved geomorphological analysis and geochronological study. Glacial landforms were dated based on the Terrestrial Cosmogenic Nuclide dating (10Be). This method is suitable for date quartz-rich materials and for the period of interest. To deduce paleoclimate conditions an analysis based on paleo ELA was developed.In the central Mérida Andes different Late Pleistocene glacier dynamics were identified. In the Mucubají and the Mucuchache valleys, successive stages of glacier stop-advance were identified during an overall glacier withdrawal. In the Gavidia and Mifafí valleys, glacier withdrawal was rapid with the highest retreat rates (between 4-7 km/ky). Morphometric features as glaciers bottom valley slopes, accumulation zone topography (glaciers cirques with steep walls), areas and orientation controlled different glaciers dynamics.Glacier advances were evidenced between 2500-4200 m. MIS 3 glaciers advances has been recognized in the Sierra Nevada. These were related to the highest runoff in the north of South America produced by the Intertropical Convergence Zone (ITCZ) and the local warm and wet climate conditions (locally named El Pedregal Interstadial). LGM glacier advances were recorded in Sierra Nevada in the Mucubají and Las Tapias between 3100-3600 m. MIS 2 Glaciers advances mainly occurred during the Oldest Dryas- El Caballo Stadial at around 17 ka. These glaciers advances correlate to the cold temperatures in the North Hemisphere and the coldest temperatures recorded in tropical ice cores.KeywordsTerrestrial cosmogenic nuclides dating, TCN, cosmogenic dating, glacial landforms, Andes Mérida, Venezuela. Pleistocene, Last Glaciation, LGM, paleo ELA, tropic paleoclimate.

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No. of bitstreams: 1 sala_me_dr_rcla.pdf: 5221486 bytes, checksum: ee17eec148cacaf5af030b574fd086eb (MD5) Previous issue date: 2018-10-22 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / O objetivo central da presente tese é identificar as variáveis conceituais, cognitivas e didático-pedagógicas que dificultam ou impedem estudantes do 6º ano do Ensino Fundamental II de compreenderem satisfatoriamente as grandes formas de relevo. Esta pesquisa desenvolveu-se a partir da constatação da persistência histórica destas dificuldades, como decorrência da relação conflituosa entre os conceitos difundidos por diversos livros didáticos e os conteúdos sistematizados no mapa das Unidades do Relevo Brasileiro. Inicia-se o texto com reflexões referentes à pertinência da concentração de tópicos do conhecimento geomorfológico apenas no 6º ano, associadas à forma pela qual são elaborados os mapas escolares de relevo e topográficos, as respectivas escalas de análise e a abordagem morfogenética do relevo, que devido à incompatibilidade cognitiva para sua compreensão no 6º ano, se torna um conteúdo apenas a ser memorizado. Como forma de delinear e intervir neste cenário, cinco exercícios presentes em livros didáticos foram investigados, para então se propor materiais que visavam oportunizar melhores condições para o ensino e aprendizagem do assunto. Para isso, foi utilizada a metodologia de Pesquisa Qualitativa, com coleta de dados em quatro escolas de Belo Horizonte/MG. Para levantamento dos dados nas escolas, foram necessárias três etapas de campo, em 2014, 2015 e 2018. A primeira etapa teve caráter diagnóstico, e forneceu elementos que subsidiaram a elaboração de exercícios aperfeiçoados para a segunda etapa, que por sua vez subsidiaram novos exercícios para a terceira etapa. Os resultados da terceira etapa indicaram que o estudo do relevo enquanto condicionante ambiental se mostrou mais eficaz do que através da compreensão dos conceitos de planaltos, planícies e depressões. Os resultados finais permitiram constatar que o ensino das formas superficiais de relevo através da denominação de suas grandes formas no Ensino Fundamental é inadequado, sendo indicada sua abordagem somente após o alcance do estágio cognitivo abstrato, que pode ocorrer entre 11 e 15 anos de idade. Constatou-se também a existência de problemas conceituais, especialmente relacionados às depressões. Paralelamente, foram realizadas entrevistas com os professores das turmas que participaram da pesquisa e com o Prof. Dr. Jurandyr Ross, que é a principal referência na inserção e disseminação do conteúdo das formas de relevo em livros didáticos da Educação Básica. Este estudo foi enriquecido com pesquisas referentes à construção conceitual e distribuição dos conteúdos geomorfológicos em livros didáticos húngaros, nos quais foi possível constatar que o relevo é trabalhado processualmente, do primeiro ao último ano escolar. O estudo se encerra anunciando a necessidade de diálogos mais profundos com a metodologia húngara, no intuito de se pensar em uma alfabetização geomorfológica processual, desenvolvida em escalas de detalhe, voltadas para a realidade discente, e cujos mapas possam ser elaborados coerentemente com as habilidades cognitivas requeridas. As formas de relevo, além de contribuírem na compreensão da origem e evolução do planeta, ajudam a promover o senso de pertencimento, cidadania e o melhor entendimento de sua significância enquanto componente cultural, socioeconômico e ambiental. / The main goal of this thesis is to identify the conceptual, cognitive and didactic-pedagogical variables that make it difficult or obstruct for students in the 6th grade of Elementary School to comprehend satisfactorily how the Brazilian great landforms are. This research was developed from the historical persistence of these difficulties, as a result of the conflictual relationship between the concepts disseminated by various didactic books and the systematized contents on the map of the Brazilian Relief Units. The text begins with reflections about the pertinence of the topics’ concentration of geomorphological knowledge only in the 6th grade, associated with the way in which the school maps of relief and topography are elaborated, the respective scales of analysis and the morphogenetic approach of the landforms, which due to cognitive incompatibility for their understanding in the 6th grade, becomes a content only to be memorized. As a way of delineating and intervening in this scenario, five exercises in textbooks were investigated, in order to propose materials that aim to provide better conditions for teaching and learning the subject. For this, a Qualitative Research’s methodology was used, with data collection in four schools in Belo Horizonte/MG. In order to collect data in schools, three field stages were necessary in 2014, 2015 and 2018. The first stage was diagnostic, and provided elements that supported the elaboration of improved exercises for the second stage, which in turn subsidized new exercises for the third stage. The results of the third stage indicated that the study of the landforms as an environmental conditioner proved to be more effective than through the understanding of the concepts of plateaus, plains and depressions. The final results showed that the teaching of the superficial landforms through the denomination of its great forms in Elementary School is inadequate, and its approach is indicated only after reaching the abstract cognitive stage, which can occur between 11 and 15 years of age. Conceptual problems, especially related to depressions, were also found. At the same time, interviews were carried out with the teachers of the groups that participated in the research and with Prof. Dr. Jurandyr Ross, who is the main reference in the insertion and dissemination of the content of landforms in textbooks of Basic Education. This study was enriched with researches related to the conceptual construction and distribution of geomorphological contents in Hungarian textbooks, in which it was possible to verify that the landforns is processed procedurally, from the first to the last school year. The study concludes by announcing the need for deeper dialogues with the Hungarian methodology, in order to think of a procedural geomorphological literacy, developed at extended scales, aimed at the student reality, and whose maps can be elaborated coherently with the required cognitive skills. The landforms, besides contributing to the understanding of the origin and evolution of the planet, help promote a sense of belonging, citizenship and a better understanding of its significance as a cultural, socioeconomic and environmental component. / CAPES: 001

GEOMORPHOLOGICAL ASPECTS OF THE OCCURRENCE OF MOLDAVITES IN THE CENTRAL EUROPE ABSTRACT: In the presented paper, geomorphological aspects of the occurrence od moldavites are evaluated. The origin od moldavites in the Miocene and position of their main finding places in Czechia is described. For studies and documentation of morphology of the surface of moldavites was used the collection of the Faculty od Science at Charles University. Special attention during field geomorphic servey of finding places of moldavites was attend to the localities between settlements Ločenice, Nesměň and Chlum nad Malší. Main features od the natural environment were identified as well as recent changes of landforms caused by prohibited and legal extraction of moldavites. All notable finding places of moldavites in the southern Bohemia are affected by these anthropogenic changes of the landscape. It is discussed that absence of moldavites in some denuded areas of the region where they are occurring can indicate a range of rocks exhumation since the upper Miocene. On the contrary, it is suggested thah morphostratigraphical significance od sporadic findings of moldavites many kilometres from primary localities is limited by a low resistance of the shape and volume of moldavites in relation to fluvial transport. However, very...

This thesis provides a description of the periglacial environment and features in the vicinity of Tiffindell Ski resort, on the slopes of Ben MacDhui (3001.2m.), the highest point of the East Cape Drakensberg, South Africa. Active and inactive periglacial features were located, mapped and described. Of particular interest were periglaciar slope deposits including gelifluction turf-banked lobes and stone lobes, and cryoturbation features including polygons and thufur. Local environmental factors, such as aspect, moisture, topography, soil texture and depth of freezing, appear to act as important controls on the spatial distribution of the periglacial features. Identification and quantification of periglacial processes in the regolith was investigated using temperature and soil moisture sensors coupled to dataloggers. Research was undertaken over a 16 month period from June 1995 to September 1996 so that comparisons between the winter conditions of 1995 and 1996 could be drawn. The Tiffindell area was observed to be characterised in the winter months by 'diurnal freezethaw days', as well as by 'ice days', 1996 experiencing colder temperatures than 1995. With more than 78% of the days from May to September 1996 being 'ice days', and simultaneously experiencing high soil moisture contents, freezing penetration to a depth of greater than 0.2m was observed to occur in the Tiffindell area, causing frost heave and gelifluction. The summer thaw of ice lenses that developed in the cold winter months caused surface movement downslope of gelifluction lobes of up to 39mm over an 18 month period, although movement declined rapidly with depth and was essentially restricted to the uppermost 130mm of the regolith. Other features such as sorted and non-sorted polygons and thufur were identified and found to be active under the present climatic conditions and depth of frost penetration at Tiffindell. Stone lobes were identified on the south and southeast-facing slopes at Tiffindell, but are apparently inactive under present climatic conditions. Their existence suggests the presence of severe seasonal frost in the past. The implications of the air and ground surface temperatures, and of seasonal frost penetration for the development of Tiffindell Ski resort were considered, and suggestions regarding their economic significance are presented.

L’environnement périglaciaire en général et les régions de permafrost en particulier, connus pour être très sensibles au changement climatique actuel, sont le sujet de beaucoup d’études sur les émissions de gaz à effet de serre. En effet, le dégel de ces milieux engendre la mobilisation d’une quantité importante de matière organique, précédemment piégée par le froid, favorisant les émissions de dioxyde de carbone et/ou de méthane. L’objectif premier, du présent travail, est de contribuer à l’étude des gaz enfermés dans certains types de glace de ces régions afin de mieux quantifier leur impact potentiel sur le climat.<p>Dans un premier temps, une analyse multiparamétrique a été menée sur deux coins de glace du nord de la Sibérie dans la cadre d’une collaboration avec l’Alfred Wegener Institut (Allemagne). Cette première approche a révélé que l’analyse conjointe de la cristallographie, de l’orientation des axes optiques, du contenu en gaz total et de la composition en gaz des coins de glace est un outil puissant, complémentaire aux analyses des isotopes stables, pour comprendre les conditions paléo-climatiques qui ont régi la construction des coins de glace. Cette étude soutient également l’hypothèse de variations spatiales importantes de l’origine des masses d’air durant les variations climatiques du Pléistocène.<p>Dans un deuxième temps, une analyse des caractéristiques de la glace annuelle de 4 lacs du nord de la Suède a été réalisée afin d’étudier le rôle de la couverture de glace sur les émissions de gaz à effet de serre. En effet, les lacs de ces régions contribuent fortement aux émissions de méthane durant la période d’eau libre et très peu d’études ont analysé la quantité de méthane emprisonnée dans la glace hivernale et relâchée au printemps. Ce projet nous a amené à établir une nouvelle classification des bulles dans la glace de lac basée sur leur contenu en méthane, leur origine, leur forme et leur densité. Il nous a également permis de montrer que plusieurs facteurs interviennent sur le contenu en gaz dans la couverture de glace :le système hydrologique, la variation de la pression atmosphérique, la variabilité des émissions et potentiellement la proximité des sédiments sont autant de facteurs qui déterminent le contenu en gaz. L’analyse de la composition des gaz a révélé que la composition observée dans la glace est sensiblement différente de celle observée durant les périodes d’eau libre. Nous avons également, pour la première fois, établit un budget des émissions de méthane relâchées par la fonte de la couverture de glace au niveau mondial.<p>Cette étude a été complétée par l’analyse des isotopes 13C des gaz des différents types de bulles de notre classification en collaboration avec l’Université d’Utrecht. Nous avons alors mis en évidence que la couverture de glace influence l’équilibre biogéochimique dans l’eau en favorisant l’oxydation du méthane en dioxyde de carbone.<p> / Doctorat en Sciences / info:eu-repo/semantics/nonPublished

This research documents the Holocene glacial history of Mount Hood, Cascade Mountains, Oregon by analyzing a set of three lateral moraines abutting Eliot Glacier, the largest glacier on the mountain. This study seeks to: 1) establish the relative ages of these lateral moraines and 2) determine if these features represent distinct glacial advances. The hypothesis is that the lateral moraines for Eliot Glacier represent three distinct periods of glacial advance based on their position relative to the current glacier and other diagnostic indicators. Soil profiles of three positions (shoulder, backslope, and footslope) on the distal side of each lateral moraine were described in the field and samples were taken from each horizon for laboratory analyses of pH and particle size. The results of the soil analysis show that the soils developing on the moraine closest to the current glacier are poorly developed and significantly younger than the other two features. The closest moraine likely dates to the Little Ice Age (600-150 YBP) and has soils with an A/C profile and a classification of Andic Cryopsamment. The soils on the middle and furthest moraines from the glacier are similar in the profile sequence (Andic Haplocryepts). Silt bulges were noted in the mid-slope pits. The furthest moraine has deeper horizons and more color development than the middle moraine. Ash layers were found in the backslope soil profile (36-51cm deep) on the middle moraine. Additional lab testing confirms the ash layers originated from Mount Hood, but no date can be assigned. The eruptive history of Mount Hood points to the Timberline eruptive period (1,500 YBP) as a likely candidate for one of the ash deposits. This evidence suggests the middle moraine was actively forming during this period and is intermediate in age between the furthest moraine and the Little Ice Age Moraine; hence, this sequence of moraines indicates three distinct periods of glacial advance in the Neoglacial.

No description available.

<p>Examinator Professor Peter Jansson, Institutionen för naturgeografi</p> / Research school for teachers on climate and environment grant 2017-06037

Permafrost is a variable in Antarctic terrestrial ecosystems, and the role it plays in the cryosphere is not well understood. There is much still to be learnt about the thermal state, physical properties, thickness and age of permafrost in Western Dronning Maud Land (WDML). Active layer dynamics and observed change over time have the potential to improve our knowledge of climate change. Understanding the effects of a warming climate on permafrost can also be of benefit to infrastructure, especially in areas with a large amount of frozen ground such as Scandinavia, Canada and Russia. Active layer and permafrost dynamics of WDML, Antarctica, are presented and discussed using data from six study sites, namely the Robertskollen, Vesleskarvet, Flarjuven, Grunehogna, Slettjfell nunataks and the Troll research station in the Jutulsessen area. Ground and ambient air temperature, as well as ground moisture data were collected for each site. An inventory of active layer and permafrost landforms was compiled, as were the frequency of cycles over the zero-degree isotherm, and the depth of the active layer. Furthermore, 3D models, geo-referenced maps and Digital Elevation Models were created of study areas with the use of an Unmanned Aerial Vehicle (UAV). Polygonal features are the most common landscape feature and are common to most of the study sites. Robertskollen has the deepest active layer at over 66cm and Slettfjell the shallowest at 9cm. A maximum recorded air temperature of 8.76°C (10/11/2014) occurred at Troll with the second highest maximum of 6.77°C (22/12/2010) recorded at Vesleskarvet. Robertskollen has the highest observable biological growth and a maximum recorded ground temperature of 22.84°C (10/01/2014). Troll and Valterkulten, registered the second and third highest ground temperatures respectively. The high ground Temperature observed for Robertskollen may be ascribed to it being the lowest altitude site. The highest number of cycles over the zero-degree isotherm was observed at Troll (11.01%), followed by Robertskollen (10.99%). For relatively warm areas, such as Robertskollen it is recommended that two metre borehole loggers are installed in order to capture a detailed understanding of the active layer. The UAV proved to be a beneficial tool for capturing aerial photographs for post fieldwork analysis and 3D modelling.