The Western branch of the East African Rift : a review of tectonics, volcanology and geothermal acitivity

Abstract

The East African Rift System (EARS) is a classic example of continental rifting and provides an excellent framework to study extensional magmatism and the evolution of several central volcanic systems that have formed along the rift from the Tertiary to Recent. Many of the volcanic structures have developed substantial high-temperature geothermal systems where the heat source is magmatic and related to central volcanoes. Detailed studies indicate that the geothermal potential in Eastern Africa is in the excess of 15,000 MWe. However, despite the high geothermal potential of EARS only Kenya has installed significant capacity of about 570 MW. Magmatism along the EARS is generally believed to be associated with mantle plume activities but the number and nature of mantle plumes is still, however, controversial. EARS is divided into two main branches, the Eastern- and Western rifts, and it is well documented that significantly greater volcanism is observed in the older Eastern rift (i.e. Ethiopia and Kenya) compared to that in the younger Western rift, where eruptive activity is, in general, restricted to four spatially distinct provinces along the rift axis. These are the Toro-Ankole in western Uganda, the Virunga and Kivu provinces along the border of the DRC with Uganda, Rwanda and Burundi, and the Rungwe volcanic field in SW Tanzania.