Evolution of the Conjugate East African-Madagascan Margins and the Western Somali Basin PDF Download

Author: Millard F. Coffin
Publisher: Geological Society of America
ISBN: 0813722268
Category : Continental margins
Languages : en
Pages : 89

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Author: Josphat K. Mulwa
Publisher: Elsevier Inc. Chapters
ISBN: 0128083972
Category : Science
Languages : en
Pages : 36

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The East African Rift System (EARS) and by extension the Davie Ridge, which is considered as the seaward extension of eastern branch (Kenya Rift Valley) of the East African Rift Valley (), are characterized by divergence whose maximum rate is estimated to be about 7mm/year (). This rate of divergence is somewhat much slower than that found at most active mid-ocean ridges or even the convergence of India–Burma plates or that between the Australian and Sunda plates (). Despite this slow rate of divergence, the East African Rift Valley and the Davie Ridge are characterized by frequent seismicity with large and shallow earthquakes occurring occasionally. Seismic reflection, gravity, and magnetic data from offshore East Africa allow the Davie Fracture Zone to be traced from 11oS to its intersection with the Kenyan coast at 2oS, constraining the relative motion of Madagascar and Africa (). Further, numerous faults and fractures probably associated with the Davie Fracture have been mapped using recent gravity and magnetic data between latitudes 2o21′S and 3o03′S and longitudes 40o08′E and 40o45′E by . Seasat-derived free-air gravity anomalies and slope/rise positive magnetic anomalies observed in shipboard data help to locate the continent–ocean boundaries (COB) off the shore of East Africa and Madagascar. Furthermore, the EARS, and precisely the Kenya Rift Valley, is characterized by ~3-km-thick sediments and normal-faulting mechanism. Deformation has been active along the Kenya Rift Valley as evidenced by high seismic activity. Surface deformation studies from SAR interferometry in the southern sector of the Kenya Rift Valley in Magadi show that it is characterized by 14cm of deformation over 10-km-long stretches (). If the Davie Ridge is an extension of the East African Rift Valley, we cannot rule out the occurrence of tsunami-generating earthquakes, which are bound to have devastating consequences on the eastern coast of Africa. Earthquakes as deep as 40km have been recorded below Davie Ridge (). However, evaluation of recent seismic data shows that magnitude 6.0–7.2 earthquakes at relatively shallow depths of 10–30km are a common occurrence along the Kenya Rift Valley and the Davie Ridge in the Mozambique Channel. The focal mechanism of these earthquakes supports what has previously been proposed that the Davie Ridge is a southward extension of the eastern arm of the EARS. The earthquake focal mechanism indicates that the Davie Ridge is characterized by predominantly normal faulting with occasional oblique faulting. Consequently, Kenya and generally the East African coast are prone to both seismic hazards on land and tsunami-generating earthquakes. This chapter begins with general overview of the seismicity in Kenya from the 1900s to the present. Seismicity in Kenya up to 1963 is mainly based on macroseismic data while that from 1963 to the present is based on data from instrumental recordings. In the past, a number of microseismic and seismicity studies in Kenya have previously been undertaken and the results from these studies are rather disjointed. In this chapter, we have made an attempt to merge all the existing results into one database from which the general seismicity, and subsequently seismic hazard in Kenya has been evaluated. The main goal of this chapter is to bring into focus the area(s) in Kenya more prone to seismic hazards either due to ground shaking occasioned by an earthquake or due to tsunami as a result of earthquakes occurring along the Davie Ridge.

Author: Douwe J. J. van Hinsbergen
Publisher: Geological Society of London
ISBN: 9781862393356
Category : Science
Languages : en
Pages : 392

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The African continent preserves a long geological record that covers almost 75% of Earth's history. The Pan-African orogeny (c. 600-500 Ma) brought together old continental kernels (West Africa, Congo, Kalahari and Tanzania) to form Gondwana and subsequently the supercontinent Pangaea by the late Palaeozoic. The break-up of Pangaea since the Jurassic and Cretaceous, primarily through opening of the Central Atlantic, Indian, and South Atlantic oceans, in combination with the complicated subduction history to the north, gradually shaped the African continent. This volume contains 18 contributions that discuss the geology of Africa from the Archaean to the present day.

Author: John J. Mahoney
Publisher: American Geophysical Union
ISBN: 0875900828
Category : Nature
Languages : en
Pages : 441

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Published by the American Geophysical Union as part of the Geophysical Monograph Series, Volume 100. Continental flood basalts, volcanic passive margins, and oceanic plateaus represent the largest known volcanic episodes on our planet, yet they are not easily explained by plate tectonics. Indeed, some are likely to record periods when the outward transfer of material and energy from the Earth's interior operated in a significantly different mode than at present. In recent years, interest in large-scale mafic magmatism has surged as high-precision geochronological, detailed geochemical, and increasingly sophisticated geophysical data have become available for many provinces. However, the sheer amount of recent material, often in the form of detailed collaborative research projects, can overwhelm newcomers to the field and experts alike as the literature continues to grow dramatically. The need for an up-to-date review volume on a sizable subset of the major continental and oceanic flood basalt provinces, termed large igneous provinces, was recognized by the Commission on Large-Volume Basaltic Provinces (International Association of Volcanology and Chemistry of the Earth's Interior), and the co-editors were charged with organizing and implementing such a volume. We hope that this volume will be valuable to researchers and graduate students worldwide, particularly to petrologists, geochemists, geochronologists, geodynamicists, and plate-tectonics specialists; it may also interest planetologists, oceanographers, and atmospheric scientists.

Author: Richard A. Geyer
Publisher: CRC Press
ISBN: 135108951X
Category : Science
Languages : en
Pages : 732

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This handbook presents advanced research and operational information about hard minerals and hydrocarbons. It provides information in an integrated, interdisciplinary manner, stressing case histories. It includes review chapters, illustrations, graphs, tables, and color satellite images that present the results of gravity, geodetic, and seismic surveys and of 3-D sea floor sub-bottom visualizations. The data was obtained using satellites, aircraft, and ships from the Atlantic and Pacific Oceans, the Gulf of Mexico, and the Caribbean Sea.Major topics addressed in these volumes include geophysical methods used to explore for hydrocarbons, advanced radiometric and electrical methods for hard mineral searches, the role of geotechnology and seismic acoustics in overcoming geological hazards in selecting drilling sites and pipeline routes, and remote sensing techniques used to determine the physical properties of hydrocarbons.

Author: Pascale Leturmy
Publisher: Geological Society of London
ISBN: 9781862392939
Category : Science
Languages : en
Pages : 374

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The Zagros fold-thrust belt (ZFTB) extends from Turkey to the Hormuz Strait, resulting from the collision of the Arabian and Eurasian plates during Cenozoic times, and separates the Arabian platform from the large plateaux of central Iran. To the east a pronounced syntaxis marks the transition between the Zagros collision belt and the Makran accretionary wedge. In the ZFTB, the Proterozoic to Recent stratigraphic succession pile is involved in huge folds, and offers the opportunity to study the stratigraphic and tectonic evolution of the Palaeo-Tethyan margin. Few recent data were widely available on the southern Tethys margin preserved in the Zagros Mountains. The Middle East Basins Evolution (MEBE) program was an excellent opportunity to go back to the field and to collect new data to better constrain the evolution of this margin. In this volume the structure of the Zagros Mountains is explored through different scales and using different methodologies.

Author: Heinz Schandelmeier
Publisher: CRC Press
ISBN: 1351445243
Category : Science
Languages : en
Pages : 622

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This volume focuses on approaches towards a better understanding of the geological, hydrogeological and paleoclimatic evolution of Northeast Africa. Among the topics discussed are Phanerozoic interplate dynamics, sedimentology and stratigraphy, and mineral deposits and metallogeny.

Author: Alan E.M. Nairn
Publisher: Springer Science & Business Media
ISBN: 1489915583
Category : Science
Languages : en
Pages : 540

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''A voluminous encyclopedia of Tethyan geology and, as such, it provides an invaluable source of information for those interested in this region, and Earth history in general...The book is a must for the libraries of universities and geologic institutions.'' --- Palaios, October 1997 Volume 8 focuses on the Tethys oceanic realm and introduces new concepts such as 'transit plates' and 'seuils lithospheriques.' Contributors include new guides to understanding the distribution of Tethyan mineral and organic resources, and present insights into the role of carbonate platforms. Chapters are abundant with maps and illustrations.

Author: David B. Stone
Publisher: Springer Science & Business Media
ISBN: 9401582068
Category : Science
Languages : en
Pages : 509

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The NATO ASI held in the Geophysical Institute, University of Alaska Fairbanks, June 17-28, 1991 was, we believe, the first attempt to bring together geoscientists from all the disciplines related to the solar system where fluid flow is a fundamental phenomenon. The various aspects of flow discussed at the meeting ranged from the flow of ice in glaciers, through motion of the solar wind, to the effects of flow in the Earth's mantle as seen in surface phenomena. A major connecting theme is the role played by convection. For a previous attempt to review the various ways in which convection plays an important role in natural phenomena one must go back to an early comprehensive study by 1. Wasiutynski in "Astro physica Norvegica" vo1. 4, 1946. This work, little known now perhaps, was a pioneering study. In understanding the evolution of bodies of the solar system, from accretion to present-day processes, ranging from interplanetary plasma to fluid cores, the understanding of flow hydrodynamics is essentia1. From the large scale in planetary atmospheres to geological processes, such as those seen in magma chambers on the Earth, one is dealing with thermal or chemical convection. Count Rumford, the founder of the Royal Institution, studied thermal convection experimentally and realized its practical importance in domestic contexts.

Author: Cristóbal Noé Aguilar
Publisher: Springer Nature
ISBN: 9811943362
Category : Science
Languages : en
Pages : 529

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This book gives insight into several aspects of the microbiology, biotechnology, and ecosystem sustainability of special and under-explored regions, that captivate human beings by their natural richness, their extensive biodiversity, the extraordinary forms of adaptation of the living beings that they inhabit, and even that keep living secrets as is the very origin of life. The chapters emphasize all aspects of biological diversity-its description, analysis, and conservation, and its controlled rational use by humankind. Also, the book is elaborated from a wide and multidisciplinary point of view. It presents reviews, research papers, comments, and research notes on biodiversity, ethnobiology, geoscience, chemistry, biological conservation, biotechnology, and ecosystem sustainability Two hotspots are the reference for this enriching book that describes details of extraordinary areas of the planet, from Cuatrociénegas, Coahuila (Mexico) to the Southern Western Ghats (India). The book will contribute to dealing with the practicalities of conservation management, economic, social, and political issues. It provides a forum for examining conflicts between sustainable development and human dependence on biodiversity in agriculture, environmental management, and biotechnology, and encourages contributions from developing countries to promote broad global perspectives on matters of biodiversity and conservation.