East African Rift
The East African Rift is an active continental rift zone that appears to be a developing divergent tectonic plate boundary in East Africa. In the past, it was considered to be part of a larger Great Rift Valley that extended north to Asia Minor. The rift is a narrow zone in which the African Plate is in the process of splitting into two new tectonic plates, called the Somali Plate and the Nubian Plate, which are subplates or protoplates.
The East African Rift runs from the Afar Triple Junction in the Afar Depression southward through eastern Africa. It is believed to run offshore of the coast of Mozambique along the Kerimba and Lacerda rifts or grabens, terminating in the Andrew Bain Fracture Zone complex, where it is believed to have its junction with the Southwest Indian Ridge.
The East African Rift consists of two main branches: the Gregory Rift and the Albertine Rift. These result from the actions of numerous normal (dip-slip) faults which are typical of all tectonic rift zones. The Eastern Rift Valley includes the Main Ethiopian Rift, running eastward from the Afar Triple Junction, which continues south as the Kenyan Rift Valley. The Western Rift Valley includes the Albertine Rift, and farther south, the valley of Lake Malawi.
The East African Rift Zone includes a number of active as well as dormant volcanoes, among them: Mount Kilimanjaro; Mount Kenya; Mount Longonot; Menengai Crater; Mount Karisimbi; Mount Nyiragongo; Mount Meru; and Mount Elgon, as well as the Crater Highlands in Tanzania. The Ol Doinyo Lengai volcano remains active, and is currently the only natrocarbonatite volcano in the world. Erta Ale is a continuously active basaltic shield volcano in the Afar Region of northeastern Ethiopia.
Discoveries in human evolution
Because the rapidly eroding highlands have filled the valley with sediments, a favorable environment for the preservation of remains has been created. The bones of several hominid ancestors of modern humans have been found here, including those of "Lucy", a partial, yet eye-opening australopithecine skeleton discovered by anthropologist Donald Johanson and dating back over 3 million years. Richard and Mary Leakey have done significant work in this region also.
More recently, two other hominid ancestors have been discovered here: a 10-million-year-old ape called Chororapithecus abyssinicus, found in the Afar rift in eastern Ethiopia; and the Nakalipithecus nakayamai, which is also 10 million years old.
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