The Nyasa-Shire Rift

Abstract

IN an earlier volume of this Journal I gave a preliminary account of the Nyasaland section of the Great Rift Valley,1 and it may be of interest at this stage to review subsequent observations in this region and to trace their bearing on the views then expressed as to the age and development of the Nyasa-Shire rift, which forms a notable feature in the majestic scenery of this part of central Africa. These later observations refer chiefly to the northern end of the Nyasa rift, the neighbouring and almost parallel Luangwa valley lying to the west, and the region traversed by the Shire rift. The Nyasa-Shire rift, forming part of the Rift Zone of eastern Africa, extends throughout the length of Nyasaland from north to south. The floor of the Nyasa rift is in part occupied by Lake Nyasa, which stands at 1550 feet but is in places over 2200 feet deep, with the result that parts of the floor lie more than 700 feet below sea-level. The Shire rift is traversed throughout by the Shire River, which forms an intermittent outlet, now active, from Lake Nyasa to the Lower Zambezi. The Nyasa rift and the greater part of the Shire rift are bounded by a high plateau ranging mainly from 3000 to 4000 feet in height, and this plateau, which is regarded as of Miocene age, is surmounted by a number of other smaller plateaus that attain to elevations usually of 6000 to 7000 feet, but sometimes as much as 8000 feet.