Gravity measurements in East Africa

Abstract

The elucidation of the structure and past history of the continent of Africa is beset with peculiar difficulties. A great part of it forms a plateau which has been above the sea since pre-Cambrian times ; thus the long series of stratified fossiliferous deposits left elsewhere in the course of geological time by the advance and retreat of the sea is absent. Instead, a great expanse of unfossiliferous gneisses and schists is exposed, overlain and intruded by a complex series of volcanic rocks, and split by a system of faults running from Lebanon to the Zambesi. It is thus not surprising that geological opinion is divided on many points, and especially on the origin and history of the Rift Valleys. A gravity survey of Eastern Equatorial Africa may therefore be expected to give information of great interest, for from the results we may obtain evidence as to the distribution of density in the outer layers of the earth, and from this we may hope to distinguish between the various hypotheses which have been put forward. Funds for the purpose of such a survey were generously provided by the Royal Society Government Grant Committee, the University of Cambridge, the Royal Geographical Society, and the Leverhulme Trustees ; and by the support of these bodies I was given the opportunity to carry out the work. For this support I am most grateful. I am also indebted to the University of Cambridge for two terms’ leave of absence, and I have had throughout the advantage of the support, encouragement, and assistance of Sir Gerald Lenox- Conyngham, F.R.S. Throughout the journey I was accompanied by my wife, whose assistance was invaluable.