The New International Encyclopædia/Great Rift Valley
GREAT RIFT VALLEY. The name given to a great depression which extends from Palestine in Asia to the southern end of Lake Tanganyika in Central Africa. The depression is formed really by a series of rift valleys which begins in the north with the Jordan and Dead Sea valleys, extending thence through the Red Sea basin to the strait of Bab-el-Mandeb, and across French Somaliland and Abyssinia to Lake Rudolf in British East Africa. Here the depression divides: one branch runs southward to beyond Lake Manyara, and the other takes a westerly course to Albert Nyanza, where it turns southward to the shores of Lake Tanganyika. The Great Rift Valley owes its origin to long parallel fissures or cracks in the earth's crust between which the strata have subsided, forming narrow, elongated troughs. In Central Africa the valley is frequently limited on either side by bare walls of rock which rise precipitously to the level of the adjoining plateau—4000 to 5000 feet above the sea. Elsewhere the evidence of faulting is not so apparent. Most of the great African lakes are situated in this valley. The formation of the fissures was accompanied by enormous volcanic activity, of which there are evidences in great sheets of lava, extinct volcanoes, and a few active cones. See Africa.