East African Rift System

Abstract

THE article entitled "How far does the Rift System extend through Africa ?" by Fairhead and Girdler1 is of great interest to geologists who are studying the structure of the African Pre-Cambrian platform, because the exact relocation of the epicentres of earthquakes could have great significance if related to known geological features. For example, in addition to the relationships suggested in the communication, the cluster of epicentres shown in their Fig. 1 at about latitude 14°S, longitude 22°E, lies on the south-westward projection of the Upemba rift beneath the overburden of the Okavango basin, and, by reference to sheet 5 of the new tectonic map of Africa2, also lies along the limit between the ancient Congo Craton and the Katangan orogenic belt; it may thus indicate recent continuation of movement along this fundamental lineament brought into prominence by Kennedy3. A second point of great interest is the NNE-SSW trending line in South Africa of six epicentres which is parallel to and about 300 km inland from the eastern coast. This mav be found to indicate recent movement on a lineament continuing the Shire and Urema grabens (ref. 2, sheet 9) to the south-south-west. Other important relationships will be apparent to geologists familiar with southern Africa. © 1969 Nature Publishing Group.