This book summarizes the geological knowledge accumulated on Afar in the last 60 years, demonstrating that it is, and will remain, a real "hot spot" for geological and geophysical research. It provides insights into the Earth processes along diverging plate boundaries, the study of both the continental and oceanic lithosphere and underlying asthenosphere, and margins and transitions including magmatic, volcanic, tectonic, sedimentary, hydrothermal and geodynamic processes. The Afar triangle is a geological depression that developed where the Gulf of Aden, Red Sea and East African Rift Valley meet. It is considered to be one of the Earth system's most important mantle plumes. In 1967, when the first expedition was organized, there was little information on the geology of the area, and even geographic base maps were lacking. However, the first satellite photographs from the Apollo and Gemini space missions offered a complete picture of the Red Sea-Gulf of Aden region, providinga new vision of the Afar triangle. The book describes the unique geological features that make Afar the only place in the world where an oceanic plate boundary with all its successive steps of development can be observed in the open air. It also presents the Afar triangle as one of the cradles of first, now extinct hominids. The Middle Awash area contains sites of several fossil discoveries, such as the well-known Lucy. The hydrothermal processes in Afar provide conditions suitable for the study of the most primitive forms of life (archaebacterial) and it is also one of the few places where significant quantities of telluric energy are available at the surface for geothermal development. Further, the area has economically interesting mineral deposits and illustrates a number of current climate change issues. In addition to providing geological information, the book shows that Afar is an area where an individual human population developed with its own language and culture, and which adapted to the rugged landscape and extremely dry and hot climate. It is a valuable resource for scientists and students, and also serves the needs of the Afar nation, currently split in three different countries as a result of recent historical events.

Contenu
Introduction.- Part I Afar: global context.- Global and regional geodynamic context.- Relief climate, people, languages and toponymy, exploration history.- Regional domes (Ethiopian and Kenyan) and mantle plume.- The EAR, Afar, Red Sea and Aden rifts.- Origin of mankind, origin of life.- Part II Afar geology.- Afar volcanic chronology.- Afar sedimentary units.- Sub-regional approach and geological field description.- The axial ranges.- The central volcanoes of Afar margins and transverse alignments.- Part III Crust, mantle, magmas and geodynamics.- Afar magmatic evolution: partial melting of the mantle and differentiation by crystal fractionation.- The recent/present volcano-tectonic events.- Afar in relation with the EAR (continental rift valley).- The Gulf of Tadjoura, penetration on land of the oceanic Aden ridge.- The Red Sea Link, and rotation of the Danakil block- Plate boundaries and microplates within Afar.- The Afar mantle plume, discussion.- Part IV Applied geology and socio-economic issues.- Thermal manifestations.- Geothermal potential and development perspective.- Mineral resources.- One Afar nation, 3 countries, a social and political issue.- Conclusion: emerged ocean, origin of mankind and life, sustainable future of the planet.