Rift Valley System
The Rift Valley System is a significant geological formation that stretches approximately 4,000 miles (6,400 kilometers) from Arabia to Mozambique, with a width varying between 18 to 60 miles (30-100 kilometers). It comprises two main branches: the Eastern or Great Rift Valley and the Western Rift Valley. The Great Rift Valley begins at the Jordan River, passing through the Dead Sea and the Gulf of Aqaba, continuing southward through Ethiopia and into Kenya, before reaching Tanzania and the Indian Ocean. In contrast, the Western Rift Valley spans from the northern end of Lake Malawi, covering several deep lakes, including Lake Tanganyika, which lies below sea level.
The rift is characterized by steep escarpments, such as the Kikuyu and Mau, which plunge significantly to the valley floor. Notably, the region is an important site for paleoanthropological discoveries, being home to some of the earliest hominid fossils. Excavations by renowned scientists like Louis and Mary Leakey and Donald Johanson have uncovered crucial evidence of early human ancestors, including the famous skeletal remains known as "Lucy." These findings suggest that the Rift Valley holds a pivotal place in understanding human evolution and the origins of Homo sapiens.
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Rift Valley System
Related civilization: East Africa.
Date: 3.5 million-c. 1 million years ago
Locale: Ethiopia, Uganda, Kenya, Tanzania, Mozambique
Rift Valley System
The Rift Valley system is a system of earth rifts extending from Arabia to Mozambique at a length of 4,000 miles (6,400 kilometers) and a width of 18 to 60 miles (30-100 kilometers). Two major branches of the system are formed by the Eastern, or Great, Rift Valley and the Western Rift Valley. The Great Rift Valley extends from the Jordan River through the Dead Sea to the Gulf of Aqaba and continues to the south into the Ethiopian Denakil Plain to Lake Turkana, Naivasha, and Magadi in Kenya. The rift moves through Tanzania to the Mozambique Plain up to the Indian Ocean near Beira, Mozambique. The Western Rift Valley comes from the northern end of Lake Malawi along Lakes Rukwa, Tanganyika, Kivu, Edward, and Mobutu Sese Seko (Albert). These lakes are deep, and the bottom of Lake Tanganyika is below sea level. Some plateaus adjacent to the rift slope upward toward the valley with an average drop of from 2,000 to 3,000 feet (600-900 meters) to the valley floor. The Kikuyu and Mau escarpments, for example, drop more than 9,000 feet (2,700 meters). Margherita Peak of the Ruwenzori Range, along the border of Uganda and Congo, is the highest point within the Western Rift Valley.
The Great Rift Valley may be best known as the locale in which the earliest hominids (evolutionary precursors to Homo sapiens, or human beings) have been discovered. The most famous of these excavations were conducted by the Leakeys (Louis, Mary, and Richard) at Olduvai Gorge in Kenya during the 1950’s and 1960’s and by Donald Johanson in the Afar Triangle. Johanson discovered Lucy, a 3-million-year-old skeleton of an early hominid, Australopithecus afarensis, in 1974 at a site called Hadar in the northern part of the valley. In 1978, in the southern part of the valley at Laetoli (Tanzania), Mary Leakey discovered hominid footprints dating to 3.5 million years ago. Other discoveries include the Taung child in 1924 (1.2 million years old), Zinjanthropus boisei, now called Australopithecus boisei, in 1959 (1.75 million years old), Homo habilis in 1972 (1.9 million years old), a boy Homo erectus in 1984 (1.6 million years old), and the “black skull” in 1985 (2.6 million years old). These and many other excavations of early hominids have led many paleontologists to conclude that human beings arose out of Africa.
Bibliography
Gregory, John W. The Great Rift Valley. London: Frank Cass, 1968.
Johanson, Donald C., Leonora Johanson, and Blake Edgar. Ancestors: In Search of Human Origins. New York: Villard Books, 1994.
Johanson, Donald C., and James Shreeve. Lucy’s Child: The Discovery of a Human Ancestor. New York: Morrow, 1989.
Oliver, Roland, and Michael Crowder, eds. The Cambridge Encyclopedia of Africa. Cambridge, England: Cambridge University Press, 1981.