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Author: Télesphore Sime-Ngando Publisher: Springer ISBN: 3319399616 Category : Science Languages : en Pages : 422
Book Description
This book represents the first multidisciplinary scientific work on a deep volcanic maar lake in comparison with other similar temperate lakes. The syntheses of the main characteristics of Lake Pavin are, for the first time, set in a firmer footing comparative approach, encompassing regional, national, European and international aquatic science contexts. It is a unique lake because of its permanently anoxic monimolimnion, and furthermore, because of its small surface area, its substantially low human influence, and by the fact that it does not have a river inflow. The book reflects the scientific research done on the general limnology, history, origin, volcanology and geological environment as well as on the geochemistry and biogeochemical cycles. Other chapters focus on the biology and microbial ecology whereas the sedimentology and paleolimnology are also given attention. This volume will be of special interest to researchers and advanced students, primarily in the fields of limnology, biogeochemistry, and aquatic ecology.
Book Description
Les compositions isotopiques de Sr, Nd et Pb des basaltes d'îles océaniques ont été mesurées de manière systématique depuis 30 ans. Les variations de ces compositions sont classiquement interprétées comme la signature du mélange entre des composants présents au sein des panaches mantelliques. Cependant elles peuvent aussi représenter des interactions entre les magmas et les réservoirs qu'ils traversent au cours de leurs remontées vers la surface. Après avoir mis en évidence les processus pouvant altérer la composition initiale d'un magma et proposer des moyens de s'en affranchir, 2 études locales sont éffectuées (îles de Sao Nicolau et de Sao Jorge, archipels du Cap Vert et des Açores). Ces deux études montrent la part importante des variations d'origine superficielle dans ces deux localités. Ces résultats sont ensuite généralisés à d'autres localités clés de la topologie mantellique et permettent de discuter d'un composant primitif ubiquiste dans les panaches mantelliques
Author: Pascal Lecroart Publisher: ISBN: Category : Languages : en Pages : 161
Book Description
Le géoïde et la profondeur des fonds océaniques présentent des variations témoins de la dynamique interne du manteau terrestre. La composition en éléments majeurs des basaltes des dorsales océaniques (morbs) dépend de la température et de la composition du manteau, elles-mêmes dépendantes de la convection mantellique. La cristallisation fractionnée a faible profondeur oblitère le signal géochimique. Ses effets sont corriges suivant un modèle base sur l'indice de fractionnement feo#/mgo. Le sodium résiduel pressente une corrélation négative avec la profondeur axiale le long des dorsales médio-atlantique et est-pacifique et avec le géoïde le long de la dorsale médio-atlantique. Ces corrélations sont significatives a plus de 99% et concernent les longueurs d'onde supérieures à 2000 km. A de telles longueurs d'onde, l'association géoïde - sodium résiduel révèle le contrôle de la convection a grande échelle sur la composition en éléments majeurs des morbs. L'absence de corrélation entre le sodium résiduel et le rapport k#2o/tio#2 utilise comme indicateur d'hétérogénéités mantelliques, est un argument en faveur d'un contrôle thermique. La topographie des fonds océaniques résulte d'une part de la présence de variations de densité dans la croute et le manteau supérieur, et d'autre part de la topographie dynamique liée a la convection mantellique. L'amplitude de la topographie dynamique est débattue tant l'erreur sur la caractérisation des anomalies superficielles de densité est importante. Le processus de fusion partielle sous les dorsales détermine la structure en densité de la croute et des couches superficielles du manteau. La teneur en sodium résiduel est fonction du taux de fusion et donne une indication des densités et des épaisseurs recherchées. La profondeur de la dorsale est calculée par compensation isostatique a partir des informations obtenues. Le long des dorsales médio-atlantique, est-pacifique et sud-est indienne, la topographie résiduelle, définie comme la différence entre la profondeur axiale observée et celle obtenue par compensation isostatique, possède une amplitude de 426 mètres r.m.s. Elle contient la topographie dynamique associée a la convection mantellique. Cette faible amplitude apporte une contrainte importante aux modèles de circulation mantellique.
Author: Télesphore Sime-Ngando Publisher: Springer ISBN: 3319399616 Category : Science Languages : en Pages : 422
Book Description
This book represents the first multidisciplinary scientific work on a deep volcanic maar lake in comparison with other similar temperate lakes. The syntheses of the main characteristics of Lake Pavin are, for the first time, set in a firmer footing comparative approach, encompassing regional, national, European and international aquatic science contexts. It is a unique lake because of its permanently anoxic monimolimnion, and furthermore, because of its small surface area, its substantially low human influence, and by the fact that it does not have a river inflow. The book reflects the scientific research done on the general limnology, history, origin, volcanology and geological environment as well as on the geochemistry and biogeochemical cycles. Other chapters focus on the biology and microbial ecology whereas the sedimentology and paleolimnology are also given attention. This volume will be of special interest to researchers and advanced students, primarily in the fields of limnology, biogeochemistry, and aquatic ecology.
Author: Atlantic Geoscience Society Publisher: Nimbus Publishing (CN) ISBN: Category : History Languages : en Pages : 220
Book Description
This book is about the history of the rocks and fossils of the Maritime Provinces of Canada (New Brunswick, Nova Scotia and PEI) over the last billion years. The book is beautifully illustrated in full colour, with original paintings of ancient vistas, over 150 photographs, and crisp explanatory diagrams and sketches.
Author: Jürgen Runge Publisher: CRC Press ISBN: 1000431150 Category : Science Languages : en Pages : 412
Book Description
This book celebrates the relaunch of the African Pollen Database, presents state-of-the-art of modern and ancient pollen data from sub-Saharan Africa, and promotes Open Access science. Pollen grains are powerful tools for the study of past vegetation dynamics because they preserve well within sedimentary deposits and have a huge diversity in ornamentation that allows different taxa to be determined. The reconstruction of past vegetation from the examination of ancient pollen records thus can be used to characterize the nature of past landscapes (e.g. abundance of forests vs. grasslands), provide insights into changes in biodiversity, and gain empirical evidence of vegetation response to climatic change and human activity. In this, the 35th Volume of "Palaeoecology of Africa", we bring together new data and extensive synthetic reviews to provide novel insights into the relationships between human evolution, human activity, climate change and vegetation dynamics during the Quaternary, the last 2.6 million years. Current and ongoing climate and land-use change is exerting pressure on modern vegetation formations and threatening the livelihoods and wellbeing of many peoples in Africa. In this book the focus is on the Quaternary because it is during this geological period that the modern vegetation formations developed into their current configurations against a backdrop of high magnitude global climate change (glacial-interglacial cycles), human evolution, and a growing human land-use footprint. In this book the latest information is presented and collated from around the African continent to parameterize past vegetation states, identify the drivers of vegetation change, and assess the vegetation resilience to change. To achieve this research from two broad themes are covered: (i) the present is the key to the past (i.e. studies which improve our understanding of modern environments so that we can better interpret evidence from the past), and (ii) the past is the key to the future (i.e. studies which unlock information on how and why vegetation changed in the past so one can better anticipate trajectories of future change). This Open Access book will provide a strong foundation for future research exploring past ecological, environmental and climatic change within Africa and the surrounding islands. The book is organized regionally (covering western, eastern, central, and southern Africa) and it contains specialized articles focused on particular topics (such as modern pollen-vegetation relationships and fire as a driver of vegetation change), as well as regional and pan-African syntheses drawing together decades of research to assess key scientific questions (including the role of climate in driving vegetation change and the role of vegetation change in human evolution). These articles will be useful to students and teachers from high school to the highest level of university who are interested in the origins and dynamics of vegetation in Africa. Furthermore, it is also meant to provide societally relevant information that can act as an inspiration for the development of sustainable management practices for the future.
Author: Télesphore Sime-Ngando
Author: Marc-Alban Millet
Author: Pascal Lecroart
Author: Télesphore Sime-Ngando
Author: William Cavazza
Author: 
Author: Atlantic Geoscience Society
Author: Jürgen Runge
Author: North East India Geographical Society. Academic Session