A major rifting episode began in the Afar region of northern Ethiopia in September 2005. Over a ten-day period, c. 2.5 km3 of magma were intruded along a 60 km-long dyke separating the Arabian and Nubian plates. Over the next five years, a further 13 dyke intrusions caused continued extension, eruptions and seismicity. This activity led to a renewed international focus on the role of magmatism in rifting, with major international collaborative projects working in Afar and Ethiopia to study the ongoing activity and to place it in a broader context. This book brings together articles that explore the role of magmatism in rifting, from the initiation of continental break-up through to full seafloor spreading. We also explore the hazards related to rifting and the associated volcanism. This work has implications for our understanding of how continents break-up and the associated distribution of resources in rift basins and continental margins.

A unique interdisciplinary approach to disaster risk research, including global hazards and case-studies, for researchers, graduate students and professionals.

Natural and human-induced environmental hazards are becoming increasingly prominent. The frequency of recorded natural disasters rose markedly during the last century, from about 100 per in the years up to 1940 to nearly 2800 during the 1990s. Africa is the only continent whose share of reported disasters has increased over the past decade. Several factors contribute to Africa’s high vulnerability to disasters. These include the high rate of population growth, food insecurity, high levels of poverty, inappropriate use of natural resources, and failures of policy and institutional frameworks. Despite the huge negative impact of natural and human-induced hazards on Africa’s development, little is done to prevent them. Disaster prevention contributes to lasting improvement in safety and sustainable livelihoods and is essential as part of integrated disaster management strategies. The provision of effective scientific input to policy formulation on various issues related to hazards and disasters is an ambitious undertaking. It requires the collaborative effort of the African scientific community to develop comprehensive long-term strategies and human capacity-building initiatives that will enable science to benefit society. This will further require: a) Building strong research and training institutions in Africa at national and regional levels; b) Facilitating the exchange of scientific information and sharing of ideas across borders; c) Strengthening the link between scientific research and policy making; d) Promoting outreach activities to build resilience to disaster risk; and e) Tapping the knowledge base of rural and urban communities. In this volume, the ICSU ROA has brought together selected African scientific researchers to share their views on policy direction for facing challenges linked to natural and human-induced hazards. The book is intended for policy advisers, environmental scientists, government officials and members of the general public with a special interest in environmental issues.

The magma-rich East African Rift System (EARS) is a modern rift zone that provides an opportunity to constrain the existing relationship between magmatism and strain in continental rifts. Within the EARS, the broadly rifted Turkana Depression has been identified as an important locus of strain. This study focused on the magmatic events in the Turkana Depression that began in the Pliocene (ca. 4 Ma) as part of a pulse of basaltic activity known as the Stratoid Phase - the last pulse of basaltic magmatism before strain was accommodated in the axial region of the Turkana Basin. This basaltic pulse began with the eruption of the widespread Gombe Stratoid Series and is followed by less voluminous basaltic activity in the form of shield volcanoes emplaced on top of the Gombe lava flows. We find that the Gombe Stratoid Series is representative of a high flux event with a complex magma plumbing system that was produced by large degrees of decompression melting of the upper mantle during a broad stretching event in Turkana. In contrast, the waning of magma flux resulted in the development of shield volcanoes subsequent to the eruption of the Gombe Stratoid Series. The timing of magmatic activity of some of the shield volcanoes suggests that there was a migration of magmatism towards Lake Turkana. Unlike the Gombe Stratoid Series lavas, we find that shield-volcano lavas require a component derived from metasomatized enriched lithospheric mantle. The contribution of this enriched component is more pronounced towards the east, coincident with a younging of magmatism in this direction. We suggest that the presence of easily fusible material in the continental lithospheric mantle in the vicinity of the Lake Turkana Basin may result in the generation of localized lithospheric melt following the broad plate stretching event that yielded the Gombe Stratoid Series. Lithospheric melts will promote the focusing of formerly broadly distributed plate stretching into a more localized region where plate melting may have occurred. We suggest that melting of enriched lithospheric mantle may account for the modern localization of strain and migration of magmatism and rifting towards the currently active volcanic centers in Lake Turkana Basin.

This dissertation examines the interplay between tectonic and magmatic processes that influence the nature of volcanically active regions. In particular, I address how faulting, fluid transport, and magma intrusion interact in a variety of settings, including continental rifts, large igneous provinces (LIPs), and monogenetic volcanic fields. In the East African Rift (EAR), I combine structural measurements and field observations with geochronology, geochemistry, and seismicity data to investigate how continental breakup initiates and evolves. Analyses of volcanic cone lineaments illustrate variations in the geometries and distributions of dike intrusions along the rift. In early stage basins (10 Ma), dikes begin to accommodate extension along the entire length of the basin. Measurements of diffuse gas flux in the EAR demonstrate that significant volumes of magmatic CO2 (>4 Mt yr−1) are rising along faults from upper mantle/lower crustal magma bodies. Over the entire EAR, this tectonic degassing (~71+/-33 Mt yr−1) contributes significantly to Earth's natural CO2 budget. Moreover, the release of magmatic volatiles assists strain localization and the development of new rift segmentation within existing half-graben depressions. Newly developing segments become kinematically linked with existing rift segments through the reactivation of rift-oblique basement fabrics. Resulting transverse faults postdate rift-parallel fault systems, indicating that preexisting weaknesses play a critical role at all stages of rift development. A regional synthesis of sill-fed dikes of the Ferrar LIP, Antarctica, and field and remote-sensing analysis of the Hopi Buttes volcanic field, Arizona, highlights the role of interconnected dike-sill systems in feeding eruptions. Measurements reveal a previously unrecognized feeder system to LIP eruptions----analogous to a "cracked lid" atop a sill network----that may be the archetypal model for LIPs that intrude sedimentary basins undergoing negligible regional extension. At Hopi Buttes, several characteristic shallow feeder systems are identified: (1) dike-dominated, (2) sill-dominated, and (3) interconnected dike-sill networks. Dike-fed eruptions are common, but sills also modulate the flow of magma toward and away from eruptive conduits, providing a novel mechanism for lateral vent migration and changes in magma-water ratios that lead to explosive volcanism.

Volcanic and Igneous Plumbing Systems: Understanding Magma Transport, Storage, and Evolution in the Earth's Crust synthesizes research from various geoscience disciplines to examine volcanic and igneous plumbing systems (VIPS) in-depth. VIPS comprise a network of magma transport and storage features in the Earth’s crust. These features include dykes, sills and larger magma bodies that form the pathway and supply system of magma beneath active volcanoes. Combining basic principles with world-class research and informative illustrations, this unique reference presents a holistic view of each topic covered, including magma transport, magma chambers, tectonics and volcanism. Addressing a variety of approaches to these topics, this book offers researchers and academics in the Earth Science fields, such as geophysics, volcanology and igneous petrology the information they need to apply the information to their own disciplines. Provides an easily understandable overview of current research on volcanic and igneous plumbing systems Includes full color illustrations to increase understanding Covers fundamental information needed to optimize comprehension Features a field example from world-class research in each chapter, including photographs and maps