Geology and the geothermal systems of the southern segment of the Kenya Rift

*Permanent address The Kenya Rift is part of the East African Rift system, which is an active continental divergent zone. The Southern segment of the Kenya Rift Valley is a unique petrographic province comprising of at least four Quaternary to Recent volcanic complexes namely Suswa, Longonot, Olkaria, and Eburru. Although these volcanoes are located only about 40 km from each other, the eruptive products show marked compositional contrasts, requiring differences in magmatic processes. The rocks are characterised by subalkaline/peralkaline trachyte and/or peralkaline rhyolite volcanism with basalts being confined to eruption sites between individual centres. The segment of the Kenya Rift has anomalously high heat flow due to shallow intrusions. Active geothermal systems are associated with the volcanic centres. This paper summarizes the geology of the southern segment of the Kenya Rift and discusses reasons that indicate greater geothermal potential for Olkaria and Eburru and promising geothermal potential for Suswa and Longonot volcanic centres all with an estimated potential of more than 1000 MWe. These include the youthfulness of the volcanic activities, large shallow magma chambers, fractured reservoir rocks, and favourable hydrogeology. Geothermal energy in Kenya is mainly utilized for generation of electricity and to a very small extent in direct use for drying pyrethrum, soil fumigation and in greenhouse heating.