Recent geophysical studies of the kenya rift valley

Abstract

This paper describes some of the recent geophysical work done in Kenya with a view to determining the structure of the crust and upper mantle in the vicinity of the Rift Valley. The principal techniques used are described briefly and include surveys of the gravity and magnetic fields, the study of the propagation of seismic waves, and measurements of heat flow and electrical conductivity. The experimental results are consistent with a model comprising the swelling of the asthenosphere into the lower part of the lithosphere under the Kenya ‘dome’. Dyke-like intrusions of hot material, probably rooted in this asthenolith appear to reach to within a few km of the surface under the floor of the rift valley and are responsible for the observed surface geothermal activity and recent volcanism. The origin of the rift valley and its apparent relationship to the global network of plate boundaries is briefly discussed but, although there are a number of plausible alternatives, no single theory has yet been accepted. Further geophysical work is needed to assist in the final clarification of a model satisfying all the geophysical evidence.